JAMB UTME - Physics - 2024

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The device used for measuring the angle of dip is the dip circle.

Let me explain this in simple terms:

The angle of dip, also known as the magnetic inclination, is the angle made by the Earth's magnetic field lines with the horizontal plane. It varies depending on where you are on the Earth's surface. In some places, magnetic field lines are nearly vertical, while in others they are more horizontal.

A dip circle is a specialized scientific instrument used to measure this angle. It usually consists of a magnetic needle that is free to rotate in the vertical plane.

When using a dip circle, you align it so that its plane is parallel to the direction of the Earth's magnetic field. Then, you read the angle at which the magnetic needle stabilizes. This is the angle of dip. The instrument's mechanism allows for accurate measurement of this angle by compensating for any external influences or inclinations.

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Friction due to air mass, also known as air resistance or drag, can be reduced by a concept called **streamlining**.

**Streamlining** refers to the shaping of an object in such a way that it allows air to flow smoothly around it, minimizing turbulence and reducing drag. When air flows smoothly over an object without much disturbance, there is less resistance, and the object can move more easily through the air.

Think of it like how a bullet or a fast-moving car is designed. They have a sleek, smooth shape that cuts through the air with minimal effort. This principle is applied in designing cars, airplanes, and even boats to enhance their efficiency and speed by reducing the friction with the air or water they move through.

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The degree of precision of a vernier caliper is actually the **smallest value** that the vernier scale can measure, which can be considered as the resolution or least count of the instrument. The degree of precision for most standard vernier calipers is 0.01 cm (or 0.1 mm). This means that the caliper can measure dimensions down to a hundredth of a centimeter.

To understand why this is the case, consider the construction of a vernier caliper:

• The main scale is similar to a ruler, usually graduated in centimeters and millimeters.
• The vernier scale, which moves with the sliding jaws, is marked such that some small fraction of its divisions aligns with one division on the main scale.

This alignment allows more precise measurements than the main scale alone. If the vernier scale has 10 divisions which coincide over a length equal to 9 divisions on the main scale, then each division of the vernier scale represents an extra 0.01 cm. Therefore, it allows measuring smaller intervals between the main scale markings very precisely.

Thus, you won't find vernier calipers with a degree of precision of 0.005 cm, 0.1 cm, or 1.0 cm as options in standard practice for precise measurement tools.

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The changes of living organisms over generations are referred to as organic evolution.

Organic evolution, also known as biological evolution, is the process through which species of organisms undergo changes over time due to genetic variations and environmental factors. This leads to the development of new traits and, over long periods, may result in the emergence of new species.

Here's a simple breakdown of the concept:

• **Genetic Variation:** Within a species, individuals have slight genetic differences, primarily due to mutations and the combination of parental genes.
• **Natural Selection:** In any given environment, some traits may offer a survival or reproductive advantage. Organisms with these traits are more likely to pass their genes to the next generation.
• **Adaptation:** Over generations, traits that confer advantages become more common in the population, leading to organisms that are better suited to their environment.
• **Speciation:** With significant changes over long periods, populations may diverge so much that they become new species.

This process is a key concept in biology and is fundamental to understanding the diversity of life on Earth. Organic evolution is distinct from other kinds of evolution mentioned, as it specifically deals with biological organisms.

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To understand the color of a red rose under a blue light, we need to consider how we perceive color. Objects appear colored because they reflect certain wavelengths of light. A red rose appears red in white light because it reflects red wavelengths and absorbs others.

When you shine blue light on a red rose, the situation changes. A blue light primarily contains blue wavelengths. Since the red rose does not have red wavelengths to reflect anymore, and it cannot reflect blue light (as it absorbs it), the rose will appear to be the absence of any reflected wavelength visible to our eyes.

This means the rose will appear black under blue light, as black is perceived when no visible light is reflected into our eyes. Thus, the color of the red rose under a blue light is black.

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To determine the angular velocity of a body whirled in a horizontal circle at a rate of 800 revolutions per minute (rpm), we need to convert this to the standard unit of angular velocity, which is radians per second (rad/s).

Here’s how you can calculate it:

• First, understand that one complete revolution is equal to 2π radians.
• The body completes 800 revolutions in one minute.

Now let's perform the conversion:

• Convert the revolutions per minute to revolutions per second:
• \( \frac{800 \text{ revolutions}}{1 \text{ minute}} \times \frac{1 \text{ minute}}{60 \text{ seconds}} = \frac{800}{60} \text{ revolutions per second} \), which simplifies to approximately \( 13.33 \text{ revolutions per second} \).
• Convert revolutions to radians by multiplying by \(2π\) radians per revolution:
• \( 13.33 \text{ revolutions per second} \times 2π \text{ radians per revolution} = 26.66π \text{ radians per second} \).

Rounding up the decimal to a consistent significant figure, the angular velocity is approximately 26.7π radians per second.

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When boiling water is poured into a thick glass tumbler, the inner surface of the glass is suddenly exposed to a much higher temperature compared to the outer surface. Glass is a poor conductor of heat, which means it does not transfer heat quickly. As a result, the inside of the tumbler becomes hot and attempts to **expand quickly**, while the outside remains cooler and does not expand at the same rate.

**This uneven expansion** creates tension between the inner and outer layers of the glass. The inner surface tries to expand but is constrained by the cooler, rigid outer surface, which isn't expanding as much or as quickly. This stress and tension can lead to cracking.

Therefore, the correct reason a thick glass tumbler cracks when boiling water is poured into it is because **the inside expands more rapidly than the outside.**

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The concept of an inclined plane is all about simplifying the forces involved in moving or holding a load. The **velocity ratio (VR)** for an inclined plane is defined as the ratio of the distance moved by the effort to the distance moved by the load. This can also be expressed in terms of the lengths involved in the triangle made by the inclined plane.

For an inclined plane placed at an angle **θ** to the horizontal, the velocity ratio is given by the formula:

VR = 1/sin(θ)

Given that the inclined plane is at an angle of **60º**:

First, find the sine of 60º:

sin(60º) = √3/2 (approximately 0.866)

Now, substitute this value into the formula for VR:

VR = 1/sin(60º) ≈ 1/0.866 ≈ 1.155

The **velocity ratio** for an inclined plane at **60º** to the horizontal is **approximately 1.155**.

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The major building block of an organism is Carbon. Let me explain why in a simple yet comprehensive manner:

Carbon is a unique element found in all living organisms. Its importance comes from its ability to form stable bonds with many other elements, including hydrogen, oxygen, nitrogen, phosphorus, and sulfur. This versatility allows carbon to act as a backbone for the building of complex organic molecules, including proteins, nucleic acids (such as DNA and RNA), carbohydrates, and lipids. These molecules are essential for the structure, function, and regulation of the body's tissues and organs.

Here's why Carbon is indispensable:

• Versatility: Carbon can form four covalent bonds with various atoms, enabling the creation of diverse and complex molecules.
• Formation of Chains and Rings: Carbon atoms can bond with each other to create long chains and rings, serving as the framework for most biomolecules.
• Compound Diversity: Because of its ability to bind with different elements, carbon forms a range of compounds, promoting the complexity and diversity of life.

In summary, Carbon is the primary building block of life due to its unique chemical properties that allow the formation of complex molecules necessary for life's structure and processes.

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A rainbow is formed through a combination of three processes: reflection, refraction, and dispersion. Let's break down each process to understand how a rainbow forms:

1. Refraction: When sunlight enters a raindrop, it bends or changes direction. This bending of light is known as **refraction**. Different colors of sunlight bend by different amounts because they have different wavelengths.

2. Reflection: Once inside the raindrop, the light gets reflected off the inside surface of the drop. This reflection sends the light back out of the raindrop at different angles.

3. Dispersion: As the light exits the raindrop, it bends again (refraction). Because each color bends by a different amount, the sunlight is spread out into its component colors, creating a spectrum. This spreading into a spectrum is called **dispersion**.

All three processes contribute to the formation of a rainbow. The combination of **refraction, reflection, and dispersion** results in the beautiful arc of colors that we see in the sky.

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 Measuring ionization current in air:
This is typically not a function of an electroscope. While it can detect charge, it does not measure ionization currents, which require specialized equipment like an ionization chamber.

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The thermal conductivity of a material is a measure of its ability to conduct heat. It is defined by the formula:

Q = k × A × ΔT/Δx × t

Where:

• Q is the heat energy conducted (in Joules)
• k is the thermal conductivity (in W/mK)
• A is the area through which heat is conducted (in square meters, m²)
• ΔT is the temperature difference (in Kelvin or Celsius, since a difference in degrees Celsius is equivalent to a difference in Kelvin)
• Δx is the thickness of the material (or the distance over which the temperature difference occurs, in meters)
• t is the time taken (in seconds)

We are given:

• Q = 288,000 J (since energy is in KJ and 1KJ = 1,000J)
• ΔT/Δx = 90 ºC/m (temperature gradient)
• t = 7,200 s

The cube has each side measuring 3 meters, so the area A of one face (since heat is conducted across two opposite faces, effectively using one face area for calculation) is:

A = 3m × 3m = 9 m²

Now, we need to solve for k (thermal conductivity):

Q = k × A × ΔT/Δx × t

288,000 J = k × 9 m² × 90 ºC/m × 7,200 s

k = 288,000 / (9 × 90 × 7,200)

Calculate the denominator:

9 × 90 × 7,200 = 5,832,000

Therefore:

k = 288,000 / 5,832,000 ≈ 0.0493 W/mK

This converts approximately to 4.93 × 10^-2 W/mK.

Therefore, the correct answer is 4.9 × 10^-2 W/mK.

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Young's modulus, denoted by E, is a measure of the stiffness of a solid material. It is defined as the ratio of stress to strain in a material that is behaving elastically. Stress is the force applied per unit area, and strain is the deformation experienced by the material in response to the applied stress.

Let's break down the dimensions for Young's modulus:

Stress: Stress is defined as force per unit area. Thus, the dimension of stress can be expressed as:

Stress = Force / Area

The dimension of force is given by mass × acceleration, i.e., Force = MLT^-2 (where M is mass, L is length, and T is time).

The dimension of area is length × length = L².

Therefore, the dimension of stress is:

Stress = (MLT^-2) / (L²) = ML^-1T^-2

Strain: Strain is the ratio of the change in length to the original length and is dimensionless because it is a ratio of two lengths.

Thus, the dimension of strain is simply 1 (dimensionless).

Since Young's modulus is the ratio of stress to strain, its dimension is the same as that of stress. Therefore, the dimension of Young’s modulus E is:

ML^-1T^-2

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A practical application of total internal reflection is found in fiber optics.

To understand this, let's break it down:

When light travels from one medium to another (such as from glass to air), it changes direction. This is known as refraction. However, there is a phenomenon called total internal reflection which occurs when light is traveling within a denser medium towards a less dense medium (like from glass to air) and hits the boundary at an angle greater than a certain critical angle. Instead of passing through, the light is completely reflected back into the denser medium.

Fiber optics technology makes use of this principle. In fiber optics, light is transmitted along the core of a thin glass or plastic fiber. The core is surrounded by another layer called the cladding. This cladding has a lower refractive index than the core, which facilitates total internal reflection. As a result, the light continuously reflects internally along the length of the fiber, allowing it to travel long distances with minimal loss.

This property is harnessed in various applications such as in high-speed telecommunication systems, medical equipment like endoscopes, and other technologies that require the transmission of data over long distances with high efficiency.

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When it comes to a model rocket, it is crucial to understand the different parts that make up the rocket and their functions:

• The Body Tube: This is the main frame of the rocket. It holds all the other components together and serves as the backbone of the rocket.
• The Nose Cone: This is the pointed part at the top of the rocket. It is designed to reduce aerodynamic drag and also aids in stabilizing the rocket during flight.
• The Fin: Fins are attached at the lower end of the rocket. They help stabilize the rocket's flight path by reducing wobble and assisting in maintaining a straight trajectory.

Now, “Not recovery devices” is listed among the options. A recovery device is actually a part of a model rocket system. Common recovery devices include parachutes or streamers that deploy after the rocket reaches its peak altitude, allowing it to return safely to the ground. Such devices are indeed part of a model rocket design.

Therefore, the option “Not recovery devices” itself is not recognized as a part of a model rocket. Instead, the sentence is stating that they are not part of the main components, which implies it's indicative rather than being the name of a component. Hence, it does not pertain to a single component like the body tube, nose cone, or fins.

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The mean acceleration of an object is determined by the change in velocity over the change in time. This is given by the formula:

Mean Acceleration (a) = (Final Velocity - Initial Velocity) / (Final Time - Initial Time)

From the velocity-time graph, we have the following points:

Initial Point: (2s, 5m/s)

Final Point: (4s, 15m/s)

Here, the Initial Velocity is 5m/s, the Final Velocity is 15m/s, the Initial Time is 2s, and the Final Time is 4s.

Plug these values into the formula:

Mean Acceleration (a) = (15m/s - 5m/s) / (4s - 2s)

Simplifying this, we get:

Mean Acceleration (a) = 10m/s / 2s = 5m/s²

The mean acceleration is therefore 5.0 m/s².

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To determine the amount of current required, we need to use Faraday's laws of electrolysis. The first law states that the mass of the substance deposited at an electrode is directly proportional to the quantity of electricity (or charge) that passes through the electrolyte.

Here, we have:

• The mass of the metal deposited, \( m \), is 0.02 kg.
• The electrochemical equivalent, \( z \), is 1.3 x 10^-7 kg/C.
• The time during which the current is applied, \( t \), is 120 seconds.

According to Faraday's first law of electrolysis, the mass (\( m \)) can be calculated by the formula:

m = z \times I \times t

Where:

• m is the mass of the substance deposited (in kilograms).
• z is the electrochemical equivalent (in kg/Coulomb).
• I is the current (in amperes).
• t is the time (in seconds).

Rearranging the formula to solve for current \( I \):

I = \(\frac{m}{z \times t}\)

Substituting the given values into the formula:

I = \(\frac{0.02 \, \text{kg}}{1.3 \times 10^{-7} \, \text{kg/C} \times 120 \, \text{s}}\)

Calculating the denominator:

I = \(\frac{0.02}{1.56 \times 10^{-5}}\)

Solving for \( I \):

I = 1282.05 \, \text{A}

Thus, the appropriate amount of current required to deposit 0.02 kg of metal in 120 seconds is approximately 1.3 x 10³ A.

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In a series resonant circuit, the current flowing in the circuit is at its maximum. Let me explain why:

In a series resonant circuit, we have a resistor (R), inductor (L), and capacitor (C) connected in series with an AC source. At a particular frequency called the resonant frequency, these circuits exhibit some unique characteristics. This resonant frequency is determined by the values of the inductor and capacitor and is given by the formula:

f₀ = 1 / (2π√(LC))

At the resonant frequency:

• The inductive reactance (X_L) and capacitive reactance (X_C) become equal in magnitude but opposite in phase. Thus, they cancel each other out.
• This causes the impedance (Z) of the circuit to be at its lowest value, equal to the resistance (R) of the circuit alone.
• Since impedance is at its minimum, according to Ohm’s law (V = IZ), the current through the circuit is at its maximum value for a given applied voltage.

Thus, in a series resonant circuit, when it is operating at its resonant frequency, the current flowing is at its maximum.

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At absolute zero temperature, which is defined as 0 Kelvin or -273.15 degrees Celsius, the energy of molecular motion ceases. This means that the molecules theoretically have minimal energy, and hence, their motion stops entirely. Therefore, the average velocity of the molecules is zero. In reality, absolute zero is a theoretical limit, and it is practically unreachable, but it serves as a concept to help in understanding the behavior of molecules at extremely low temperatures. Thus, under this theoretical condition, the average motion of molecules would be nonexistent. In summary, the average velocity of the molecules at absolute zero is zero.

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Inbreeding is the process where closely related individuals, like cousins or siblings, mate and produce offspring. **This practice is highly discouraged in humans for several reasons, but a significant concern is the potential for an outbreak of hereditary diseases.**

Here’s why inbreeding is problematic:

• Humans carry genes in pairs, and some of these genes might be recessive, meaning they only show their effects if an individual inherits two copies of the same gene (one from each parent). These genes might cause diseases or other health issues.
• When two closely related individuals mate, the chance of both carrying the same recessive genes is **higher**. This increases the likelihood that their offspring will inherit these genes, leading to hereditary diseases. **This genetic similarity can result in a higher risk of disorders such as cystic fibrosis, sickle cell anemia, and Tay-Sachs disease**.
• While some may argue that inbreeding could lead to other issues, such as dwarfism or higher death rates in newborns, the primary scientific concern backed by genetics is the increased susceptibility to hereditary diseases.

Therefore, **to promote genetic diversity and reduce the risk of hereditary diseases in offspring, inbreeding is discouraged in human populations**. This way, offspring are less likely to inherit harmful genetic combinations that can lead to health problems.

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In insects, the structure responsible for the exchange of gases is the tracheae. Insects have a unique respiratory system where air is taken in through tiny openings called spiracles located on the surface of their body.

The air then travels directly into a network of tubes known as the tracheae. The tracheae branch out extensively throughout the insect's body, allowing oxygen to diffuse directly to the insect's tissues and cells. The carbon dioxide produced in the cells travels back through the tracheae and exits the body through the spiracles.

Other structures like the skin, Malpighian tubules, and flame cells have different functions:

• Skin: Insects do not use their skin for gas exchange like some other animals do; their skin is generally designed to protect them from environmental elements.
• Malpighian tubules: These are involved in the excretory system of insects, helping to remove waste products from their bodies.
• Flame cells: These are structures found in certain flatworms and are part of their excretory system; they are not present in insects.

Thus, the correct answer is the tracheae as they specifically enable the exchange of gases in insects.

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To calculate the quantity of heat absorbed or released by a substance, we can use the formula:

Q = C × ΔT

where:

• Q is the quantity of heat.
• C is the thermal capacity of the substance.
• ΔT is the change in temperature.

Given:

• C = 400 J/°C
• Initial temperature = 60°C
• Final temperature = 80°C

First, calculate the change in temperature:

ΔT = Final temperature - Initial temperature = 80°C - 60°C = 20°C

Now, substitute the values into the formula to find the quantity of heat:

Q = 400 J/°C × 20°C

Calculate the answer:

Q = 8000 J

Since the options provided are in kilojoules (KJ), we need to convert joules (J) to kilojoules (1 KJ = 1000 J):

Q = 8000 J ÷ 1000 = 8 KJ

Therefore, the quantity of heat for the copper rod, given the specified conditions, is 8 KJ.

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Water is not suitable for use as a thermometric liquid because:

a) It wets glass: This can cause issues with reading the level of the liquid.
b) It needs to be coloured: Water is typically clear, making it difficult to see the level without coloring.
c) It has a low density: This can affect the sensitivity and accuracy of the thermometer.

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To solve the problem, let's first understand the concept of efficiency in this context. Efficiency refers to the ratio of the useful power output to the total power output of a system. In simpler terms, it tells us how much of the power provided by the cell is being effectively used by the resistor, X.

Given that the cell has an internal resistance (r) of 2Ω and we need the efficiency to be 75%, we will follow these steps:

• The total resistance in the circuit is the sum of the internal resistance and the resistance of the resistor X, so it is (r + X).
• Efficiency is given by the formula:

Efficiency (%) = (R / (R + r)) * 100

Where:

• R is the resistance of resistor X.
• r is the internal resistance of the cell.

According to the problem, efficiency is 75%, so:

(X / (X + 2)) * 100 = 75

First, let’s eliminate the percentage by dividing both sides by 100:

(X / (X + 2)) = 0.75

Now, let's solve for X:

1. Multiply both sides by (X + 2):

X = 0.75 * (X + 2)



2. Distribute the 0.75:

X = 0.75X + 1.5



3. Subtract 0.75X from both sides:

0.25X = 1.5



4. Finally, divide by 0.25:

X = 1.5 / 0.25



5. Solve for X:

X = 6 Ω

Hence, for the cell to have an efficiency of 75%, the value of the resistor X must be 6Ω.

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According to the kinetic theory of gases, the pressure exerted by a gas on the walls of its container relates to the behavior and movement of its molecules. To understand how this pressure forms, let's explore the following essential concepts.

Molecules in a gas move rapidly and randomly in all directions. When these molecules collide with the walls of their container, they exert force due to the change in momentum during these collisions. The frequency and force of these collisions contribute directly to the pressure experienced by the container walls.

The **pressure** exerted by the gas can be described in terms of the rate of change of momentum imparted by the walls per second per unit area. This means that pressure is determined by considering how fast and how much the momentum of the gas molecules changes when they bounce off the container's walls, spread over a specific area and over time. In simpler terms, the faster and more frequently molecules hit the walls, and the higher their change in momentum, the greater the pressure is.

This explanation can be directly associated with the statement: "rate of change of momentum imparted by the walls per second per unit area", which accurately describes the concept of pressure in the context of the kinetic theory of gases.

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To find the density of the fluid, we need to apply the principle of floatation, which states that the weight of the fluid displaced by the submerged part of the object is equal to the weight of the object. Let's walk through the steps:

Step 1: Understand the volume submerged

The hydrometer has a total volume of 2y x 10^-5 m³. It floats with 20% of its volume above the fluid. Hence, 80% of its volume is submerged in the fluid.

Submerged Volume, V_sub = (0.80) x (2y x 10^-5 m³) = 1.6y x 10^-5 m³

Step 2: Apply the principle of floatation

The weight of the fluid displaced equals the weight of the hydrometer.

Weight of hydrometer = Mass x Gravity = y kg x g (where g is the acceleration due to gravity). For the purpose of calculations, g can be considered as 9.81 m/s².

Weight of displaced fluid = Density of fluid (ρ_fluid) x Submerged Volume x g

According to the principle of floatation:

y x g = ρ_fluid x 1.6y x 10^-5 m³ x g

g is common on both sides and can be canceled out:

y = ρ_fluid x 1.6y x 10^-5

Step 3: Solving for the density of the fluid

ρ_fluid = y / (1.6y x 10^-5)

The y on both numerator and denominator cancels out:

ρ_fluid = 1 / (1.6 x 10^-5)

ρ_fluid = 6.25 x 10⁴ kg/m³

Thus, the density of the fluid is 6.25 x 10⁴ kg/m³.

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When a bus is accelerating, it is primarily changing its velocity. This is because velocity is a vector quantity, which means it includes both the speed and the direction of the object's movement. Acceleration refers to any change in this velocity. Therefore, the bus could be increasing its speed, decreasing its speed (which is also known as deceleration), or changing its direction. All these aspects involve a change in velocity.

Let's break it down further:

Changing its Speed: If the bus is speeding up or slowing down, it results in a change in the magnitude of its velocity, contributing to acceleration.

Changing its Direction: Even if the bus maintains a constant speed, if it changes direction (like taking a turn), its velocity is altered because direction is a part of velocity. This results in acceleration.

Changing its Position: While a change in position happens during acceleration, it is not the defining feature of acceleration. An object can change its position even if it is moving with constant velocity and not accelerating.

So, the key component here for acceleration is the change in velocity, which encompasses changes in speed, direction, or both.

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A rectifier is a device that changes alternating current (A.C) to direct current (D.C). Alternating current is the type of electrical current that changes direction periodically, while direct current flows in a single, constant direction.

Rectifiers are essential in numerous electrical devices, particularly those that require a stable and consistent power supply. For example, most electronic devices like mobile phone chargers, laptop adapters, and televisions operate on D.C. power, and rectifiers convert the household A.C. power supply to D.C. so that these devices can function properly.

In summary, a rectifier converts A.C., which is alternating power supply, into D.C., which is a steady flow of electricity in one direction, making it usable for electronic devices and various applications that require direct current.

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To calculate the power of an object, we need to use the formula for power in terms of work done over time. The formula is:

Power (P) = Work Done (W) / Time (t)

First, let's find the work done on the object. Work done can be calculated using the formula:

Work Done (W) = Force (F) × Distance (d)

Given:

• Force (F) = 50 N
• Distance (d) = 500 cm = 5 m (Note: We need to convert the distance from centimeters to meters because the unit of force is in newtons, and 1 m = 100 cm)

Substituting the values into the formula for work done, we get:

Work Done (W) = 50 N × 5 m = 250 Joules

Next, we consider the time it took for the object to move this distance:

• Time (t) = 1 s

Now, substituting the work done and time into the power formula:

Power (P) = 250 Joules / 1 s = 250 Watts

Thus, the power of the object is 250 Watts.

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The unit of impedance is Ohm, which is symbolized by the Greek letter Ω (Omega). In electrical circuits, impedance (Z) is a measure of opposition that a circuit offers to the passage of electric current when a voltage is applied. It is similar to resistance but extends to alternating currents (AC) and contains the effects of resistance as well as reactance (which accounts for capacitors and inductors).

Just like resistance, the unit of impedance is the ohm because they measure similar concepts; however, impedance also accounts for phase shifts between voltage and current, which are not considered in simple resistance. Ohm's Law is used in AC circuits as Z = V/I, where Z is impedance, V is voltage, and I is current. This relationship shows why the unit of impedance is the same as that of resistance.

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The diagram is that of the virus. Viruses are obligate parasites, meaning they can't produce their own energy or proteins. They enter the host cell and use the cell's machinery to make their own nucleic acids and proteins. Viruses also use the host cell's lipids and sugar chains to create their membranes and glycoproteins. This parasitic replication can severely damage the host cell, which can lead to disease or cell death. They usually enter your body through your mucous membranes. These include your eyes, nose, mouth, penis, vagina and anus.

Viruses are a unique type of organism that are not plants, animals, or bacteria. They are often classified in their own kingdom. However, for the sake of the question, since most of their attributes and metabolic activities are more of the bacteria, we'll go with option A - Monera

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An insulator is a material that has a very large energy gap between its valence band and conduction band. To understand this, let's first consider the concept of energy bands: In materials, electrons exist in different energy levels. These levels form bands called the valence band and the conduction band. A material is classified based on the size of the energy gap between these bands.

• Insulator: The energy gap is very large, which means electrons in the valence band require a lot of energy to jump to the conduction band where they can freely move. Because of this large gap, insulators do not conduct electricity well.
• Conductor: The valence band and conduction band overlap or have a very small gap, so electrons can move freely without requiring significant additional energy. Conductors actively conduct electricity.
• Semiconductor: The energy gap is moderate, which means some energy is required for electrons to move from the valence band to the conduction band. Semiconductors can conduct electricity under certain conditions, like when energy (in the form of heat or light) is provided.
• Intrinsic semiconductor: This is a pure type of semiconductor with no added impurities. It behaves like a semiconductor, having a moderate energy gap.

Thus, insulators have a very large energy gap band, making them poor conductors of electricity.

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The magnetic force on an electron in a magnetic field (F) = q v Bsinθ $\theta$

B = 10T, q =  3 x 107 ${}^7$m/, θ $\theta$ = 60º and q =  1.6 x 10−19 ${}^{-19}$C

F =  1.6 x 10−19 ${}^{-19}$ x 3 x 107 ${}^7$ x 10 x sin 60º ≊ $\approxeq$ 4.162 × 10−11 ${}^{-11}$N

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The power of a lens is a measure of its ability to converge or diverge light. It is defined as the reciprocal (or inverse) of the focal length of the lens. The formula for calculating the power (P) of a lens in diopters (D) is given by:

P = 1/f

where:

• P is the power of the lens in diopters (D).
• f is the focal length of the lens in meters.

In this case, the focal length given is 20 cm. To apply the formula, we first need to convert this focal length into meters because the diopter is the reciprocal of the focal length in meters:

f = 20 cm = 0.20 m

Now, substitute the focal length in meters into the formula for power:

P = 1 / 0.20

P = 5.00 D

Thus, the power of the convex lens is 5.00 diopters. This indicates that the lens is capable of converging light at a distance of 5.00 meters.

Détails de la réponse

In physics, the concept of work is defined as the process of energy transfer that occurs when a force makes an object move. The conditions for work to be done are:

• A force must be applied: There must be a force exerted on an object.
• The object must move: The object on which the force is applied must move from its original position.
• The movement must be in the direction of the force: The movement of the object should be in the direction of the applied force.

Now, let's evaluate each scenario:

A man supports a heavy load on his head with hands: In this case, although the man is applying a force upward to support the load, the load does not move in the direction of the force he is exerting (upward). Hence, no work is done.

A woman holds a pot of water: Similar to the first scenario, the woman applies an upward force to hold the pot. However, the pot remains stationary, and there is no movement in the direction of the force. Thus, no work is done.

A boy climbs onto a table: Here, as the boy climbs, he applies a force to move himself upward onto the table. The movement is in the direction of the upward force he is applying. Therefore, work is done.

A man pushes against a stationary petrol tanker: In this scenario, although the man is applying a force to the tanker, it does not move. Because there is no movement in the direction of the force, no work is done.

Détails de la réponse

The main feature of trees in the savanna habitat is the possession of thick, corky bark. The savanna is characterized by a distinct wet and dry season. During the dry season, fires are common as dry grasses and leaves become highly flammable. To adapt to this environmental condition, many trees in the savanna have developed a thick, corky bark which helps protect them against these frequent fires. This bark acts as an insulator, shielding the vital inner tissues of the tree from the heat of the flames. Additionally, this adaptation helps the trees retain moisture, which is crucial during the arid months when water is scarce.

Détails de la réponse

To find the apparent weight of a man of mass 60 kg standing in a descending lift, we first need to understand the concept of apparent weight. Apparent weight is the force that the man feels as his weight due to the reaction of the lift floor on him. When the lift accelerates, the apparent weight changes from his actual weight.

In this case, the lift is descending with a constant velocity of 3 m/s². Since the acceleration is downward, it means the lift is accelerating negatively compared to an upward acceleration.

The formula to find the apparent weight (W_apparent) when in a lift is:

W_apparent = m(g - a)

Where:

• m is the mass of the man, which is 60 kg
• g is the acceleration due to gravity, approximately 9.8 m/s²
• a is the acceleration of the lift (3 m/s² downward)

Substituting these values into the formula, we get:

W_apparent = 60 (9.8 - 3)

Calculating further:

W_apparent = 60 × 6.8

W_apparent = 408 N

The closest option to 408 N in the answers provided is 420 N. Therefore, the correct answer is 420 N.

Détails de la réponse

When you push a wheelbarrow inclined at an angle to the horizontal, the applied force can be divided into two components: a **horizontal component** and a **vertical component**. To find the horizontal component of the force, you need to use the concept of resolving vectors.

The force of 150N is acting at an angle of 60º to the horizontal. The horizontal component of this force can be calculated using the cosine of the angle. The formula to determine the horizontal component \( F_{\text{horizontal}} \) is given by:

F_horizontal = F_applied \times \cos(\theta)

Where:

• F_applied is the magnitude of the applied force, which is 150N.
• \(\theta\) is the angle of inclination to the horizontal, which in this case is 60º.

Substitute the values into the formula:

F_horizontal = 150N \times \cos(60º)

We know that \(\cos(60º)\) equals 0.5.

Therefore:

F_horizontal = 150N \times 0.5 = 75N

Thus, the **horizontal component** of the applied force is 75N.

Détails de la réponse

Hot wire ammeters measure current by detecting the heat produced in a wire due to the electric current flowing through it.

Détails de la réponse

To determine what the galvanometer is converted to in the described scenario, let’s first understand how a galvanometer can be transformed into different measuring devices:

1. Galvanometer to Voltmeter: To convert a galvanometer into a voltmeter, a high resistance (known as a multiplier) is connected in series with the galvanometer. This high resistance ensures that the voltmeter can measure a wide range of voltages without drawing significant current from the circuit.

2. Galvanometer to Ammeter: To convert a galvanometer into an ammeter, a low resistance (called a shunt) is connected in parallel with the galvanometer. This allows the majority of the current to pass through the shunt, enabling the ammeter to measure high currents without damaging the galvanometer.

Since the problem statement does not specify any additional details, a general observation is that a galvanometer is commonly converted into an ammeter using a shunt, especially in basic electrical circuits where current measurement is necessary. Therefore, from the options provided, **the galvanometer is most likely converted to an ammeter**.

**In summary**, if a low resistance is added in parallel with the galvanometer, it becomes an ammeter, while adding a high resistance in series would convert it into a voltmeter. Since the context commonly involves conversion for current measurement, the provided diagram likely represents a galvanometer converted into an ammeter.