JAMB UTME - Physics - 2024

Antwoorddetails

The dimension of power in physics is expressed in terms of the base units of mass (M), length (L), and time (T). Power is the rate at which work is done or energy is transferred over time, and it has the unit of watt (W) which is equivalent to one joule per second.

To derive the dimension of power:

1. Work has the dimension of energy, which is force applied over a distance. The dimension of work (or energy) is M L² T^-2 because force has the dimension M L T^-2 and distance adds another L.

2. Since power is work done per unit time, you would divide the dimension of work by time (T).

Thus, the dimensional formula for power is:

M L² T^-3

Antwoorddetails

To solve this problem, we first need to understand the principle behind a potentiometer. A potentiometer is a device used to measure the electromotive force (e.m.f) of a cell by comparing it with a known voltage. The balance length on a potentiometer corresponds to a proportional measurement of the e.m.f.

Let's denote:

- \( V_1 \): the e.m.f of the first cell = 3.06V

- \( l_1 \): the balance length for the first cell = 75 cm

- \( V_2 \): the e.m.f of the second cell = 2.295V

- \( l_2 \): the balance length for the second cell (which we need to find)

The basic relationship for a potentiometer is given by:

\( V_1 / V_2 = l_1 / l_2 \)

Substituting the given values:

\( 3.06 / 2.295 = 75 / l_2 \)

We need to solve for \( l_2 \):

\( l_2 = (2.295 \times 75) / 3.06 \)

Now, calculating the above expression:

\( l_2 = 171.975 / 3.06 \approx 56.26 \) cm

Therefore, the new balance length for the cell with an e.m.f of 2.295V is approximately 56.26 cm.

Antwoorddetails

The average translational kinetic energy of gas molecules is directly related to the temperature of the gas. This relationship is based on the principles of kinetic molecular theory, which explains the behavior of gas molecules in terms of their motion.

Let's break this down simply:

1. Temperature and Kinetic Energy:

The average translational kinetic energy of gas molecules is given by the equation:

\( KE_{avg} = \frac{3}{2} k_B T \)

where \( KE_{avg} \) is the average translational kinetic energy, \( k_B \) is the Boltzmann constant, and \( T \) is the absolute temperature in Kelvin. This formula shows that the kinetic energy is directly proportional to the temperature.

2. What This Means:

As the temperature of a gas increases, the molecules move faster, which increases their translational kinetic energy. Conversely, as the temperature decreases, the molecules slow down, resulting in lower kinetic energy.

It is important to note that this relation is independent of the pressure and the number of moles of the gas. While pressure and the number of moles do affect the overall behavior of a gas, they do not directly influence the average translational kinetic energy of individual molecules.

Therefore, the correct explanation is that the average translational kinetic energy of gas molecules depends on temperature only.

Antwoorddetails

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.

Antwoorddetails

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.

Antwoorddetails

To determine the effort needed to lift a load using a machine, we first need to understand some key concepts: **Load**, **Effort**, **Velocity Ratio** (VR), and **Efficiency**.

1. **Load** is the force or weight that needs to be lifted by the machine. In this case, the load is 300N.

2. **Velocity Ratio (VR)** is the ratio of the distance moved by the effort to the distance moved by the load. Given here as 2.

3. **Efficiency** of a machine is expressed as a percentage and is the ratio of the useful work output to the input work done by the effort. Here, the efficiency is 60% or 0.60 as a decimal.

The formula to calculate the **Effort** is derived from the relationship between these factors:

\[ \text{Efficiency} = \frac{\text{Mechanical Advantage (MA)}}{\text{Velocity Ratio (VR)}} \]

Where:

\[ \text{Mechanical Advantage (MA)} = \frac{\text{Load}}{\text{Effort}} \]

From the above, we have:

\[ \text{MA} = \text{VR} \times \text{Efficiency} \]

Replacing with the given values:

\[ MA = 2 \times 0.60 = 1.2 \]

Now, calculate the **Effort** using the relation:

\[ \text{Effort} = \frac{\text{Load}}{\text{MA}} \]

\[ \text{Effort} = \frac{300N}{1.2} = 250N \]

Therefore, the **Effort** needed to lift the load is 250N.

Antwoorddetails

The elliptical shape of the Earth: The Earth is not a perfect sphere; it is slightly flattened at the poles and bulging at the equator. This shape causes variations in gravitational acceleration.

Antwoorddetails

When you insert a sheet of an insulating material between the plates of an air capacitor, the capacitance will increase.

Here's why:

• Capacitance is a measure of a capacitor's ability to store charge per unit voltage across its plates.
• The formula for capacitance (C) is:

C = ε₀ * (εr) * (A/d)

• Where:
  • ε₀ is the permittivity of free space (a constant).
  • εr is the relative permittivity (also known as the dielectric constant) of the material between the plates.
  • A is the area of one of the plates.
  • d is the separation between the plates.
• When an insulating material (also known as a dielectric) is inserted between the plates, its εr is greater than that of air (which is 1).
• This increases the overall capacitance of the capacitor since the product of ε₀ and εr is larger than ε₀ alone.

Therefore, inserting an insulating material as a dielectric enhances the capacitor's ability to store charge, ultimately resulting in an increase in capacitance.

Antwoorddetails

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

Antwoorddetails

A non-rechargeable cell, commonly known as a primary cell, is a type of chemical battery that is designed to be used once until the chemical reactions that produce electricity are exhausted. After this point, the cell cannot be reversed or recharged.

In the given examples, the dry leclanche cell is a well-known example of a non-rechargeable cell. It is commonly used in everyday devices like remote controls, wall clocks, and torches. This cell type utilizes zinc and manganese dioxide as electrodes and relies on a moist paste of ammonium chloride for the electrolyte.

The other examples, such as nickel iron, mercury cadmium, and lead-acid, involve rechargeable cells (secondary cells) that are specifically designed to endure multiple charges and discharges throughout their useful life. Thus, unlike the dry leclanche cell, these can be recharged after use.

Therefore, the dry leclanche cell is an ideal example of a non-rechargeable cell because it can only be used once. After depletion, it cannot be recharged or reused.

Antwoorddetails

A photometer is an instrument designed to measure the intensity of light. It is used to determine how much light is received over a particular area. Photometers are vital in various fields such as photography, astronomy, and laboratory science for ensuring that light levels are appropriate for specific applications.

The device operates by assessing the brightness or illumination coming from a light source and comparing it with a standard light. The measurement can be displayed in different units such as lumens or lux, depending on the context of the measurement.

While photometers are focused on the intensity of light, they do not measure kinetic energy of liberated electrons, the frequency of light, or the wavelength of light. These quantities are measured using other specialized instruments, such as spectrometers or frequency analyzers.

Antwoorddetails

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.

Antwoorddetails

To solve this problem, we need to understand the relationship between tension and frequency in a sonometer wire. The frequency of a vibrating string, such as one in a sonometer, is directly proportional to the square root of the tension in the string. Mathematically, this relationship is expressed as:

f ∝ √T

Where f is the frequency and T is the tension. In the given problem, the original frequency is 50 Hz, and the tension is increased to four times its original value. Let's analyze how this change in tension affects the frequency:

- Original tension = T

- New tension = 4T

Substitute the new tension into the formula:

f_new = 50 Hz × √(4T/T)

Simplify the equation:

f_new = 50 Hz × √4

f_new = 50 Hz × 2

f_new = 100 Hz

Thus, when the tension is four times the original tension, the new frequency of the sonometer's fundamental note becomes 100 Hz.

Antwoorddetails

The tangential force acting on an object that opposes it from sliding freely on the adjacent surface is called the friction force.

Let me explain each of the options to clarify why friction force is the correct answer:

• Normal force: This is the force exerted by a surface perpendicular (at a right angle) to the object resting on it. It supports the weight of the object, stopping it from passing through the surface. It is not tangential and does not oppose sliding; rather, it acts perpendicular to the surface.
• Friction force: This is the force that acts parallel to the surface contact between two objects or surfaces. It arises when one object tries to move over another. The friction force acts to oppose that movement, providing the necessary resistance to prevent sliding.
• Weight: This is the gravitational force acting downwards due to the mass of an object. It does not act tangentially on the surface but directly downwards towards the center of the Earth.
• Upthrust: Also known as buoyant force, this is the upwards force experienced by an object when it is immersed in a fluid (liquid or gas). It is responsible for the object floating or being pushed up, and is not related to tangential force or friction.

In summary, friction force is the force that acts to oppose sliding between surfaces in contact and acts tangentially, making it the correct answer.

Antwoorddetails

The diagram in the image represents the urinary system, as indicated by the correct answer. The urinary system includes the kidneys, ureters, bladder, and urethra, which are responsible for filtering blood and excreting waste in the form of urine.

Main Parts of the Urinary System:

1. Kidneys – Filter waste and excess fluids from the blood to form urine.

2. Ureters – Tubes that carry urine from the kidneys to the bladder.

3. Urinary Bladder – Stores urine before it is expelled from the body.

4. Urethra – A tube that allows urine to exit the body.

This system plays a crucial role in maintaining the body's fluid balance and removing waste products.

Antwoorddetails

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.

Antwoorddetails

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.

Antwoorddetails

When a body moves in a straight line from one point, such as point P, to another point, such as point Q, the motion is called Translational Motion. This kind of motion refers to an object moving along a path in which every part of the object takes the same path as a reference point. This means that if you follow any point on the body, it covers the same amount of distance in the same time frame as any other point.

Let's break down the other options:

• Rotational Motion: This occurs when an object spins around an internal axis. For example, the rotation of the Earth on its axis is a rotational motion.


• Simple Harmonic Motion: This is a type of periodic motion where the restoring force is directly proportional to the displacement. An example of this is a pendulum swinging back and forth.


• Circular Motion: This occurs when an object moves along a circular path. For instance, the motion of the planets around the sun is circular motion.

In conclusion, since the body is moving from point P to point Q along a straight line, it exhibits Translational Motion.

Antwoorddetails

The part of the inner ear that is responsible for hearing is the cochlea.

The inner ear is a complex structure, and each of its components serves different functions. Let me break it down further:

• Cochlea: This is a spiral-shaped, fluid-filled structure that resembles a snail shell. It is the main organ responsible for hearing. Sound waves enter the ear, travel through the ear canal, and cause the eardrum to vibrate. These vibrations are then transmitted to the cochlea through tiny bones in the middle ear. Inside the cochlea, these vibrations create waves in the fluid, stimulating tiny hair cells. The movement of these hair cells converts the sound waves into electrical signals, which are sent to the brain through the auditory nerve, allowing us to perceive sound.


• Sacculus and Utriculus: These structures primarily deal with balance rather than hearing. They are part of the vestibular system, which helps the body maintain its balance and spatial orientation.


• Ampullae: These are located in the semicircular canals of the inner ear and also play a role in balance. They contain sensory hair cells that detect rotational movement of the head.

Thus, the cochlea is the crucial component of the inner ear responsible for converting sound vibrations into nerve signals, making it central to the process of hearing.

Antwoorddetails

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.**

Antwoorddetails

When we say that the displacement of a car is proportional to the square of time (d ∝ t²), it indicates a relationship between displacement (d) and time (t). This relationship is characteristic of motion where there is constant acceleration. Essentially, it means that the car is not moving at a constant speed (velocity) but is accelerating at a constant rate.

The mathematical representation of this scenario can be expressed using the formula for displacement under uniform acceleration:

d = ut + (1/2)at².

In this equation:

• d = displacement
• u = initial velocity (which could be zero)
• a = acceleration
• t = time

When the displacement is directly proportional to the square of time (d ∝ t²), it implies that the second term of the equation, which contains the (1/2)at² part, dominates the relationship. Thus, the initial velocity (u) is typically zero or negligible, making the entire displacement dependent on how time squared interacts with acceleration.

Therefore, the car is moving with uniform acceleration.

Antwoorddetails

The diaphragm in a camera is similar to the iris in the human eye.

Here's a simple explanation:

• Both the diaphragm in a camera and the iris in the eye control the amount of light that enters. The diaphragm adjusts the size of the aperture, which is the opening that allows light to hit the camera's sensor.
• Similarly, the iris adjusts the size of the pupil, which is the opening that allows light to enter the eye and reach the retina.
• The camera's diaphragm is responsible for creating different aperture sizes, just as the iris changes the size of the pupil in different lighting conditions.
• In bright light, both the diaphragm and the iris make their respective openings smaller to reduce the amount of light entering, protecting the camera's sensor and the eye's retina respectively.
• Conversely, in low light conditions, both open wider to allow more light in, enhancing clarity and visibility.

In summary, the iris acts like a natural diaphragm, regulating the light that passes through the eye, much like the diaphragm does in a camera.

Antwoorddetails

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.

Antwoorddetails

To calculate the monthly electrical bill, we first need to determine the total energy consumption of the household in kilowatt-hours (kWh). Here are the steps:

1. Calculate the total power consumption of the appliances daily:

• The appliances' power ratings are 80W, 100W, and 120W.
• Total power consumption: 80W + 100W + 120W = 300W.

2. Convert the daily power consumption from Watts to kilowatts (kW):

• Since 1kW = 1000W, the daily power consumption in kW is 300W / 1000 = 0.3 kW.

3. Calculate the energy used daily in kWh:

• The appliances are used for 6 hours daily.
• Energy used daily: 0.3 kW * 6 hours = 1.8 kWh.

4. Calculate the monthly energy consumption:

• An average month is 31 days.
• Monthly energy consumption: 1.8 kWh/day * 31 days = 55.8 kWh.

5. Calculate the cost based on the rate:

• The cost of electricity is ₦24.08 per kWh.
• Monthly electricity cost: 55.8 kWh * ₦24.08 = ₦1343.664.

Therefore, the monthly electrical bill is approximately ₦1343.66k.

Antwoorddetails

To calculate the distance between two objects based on the gravitational force acting between them, we need to use the formula for gravitational force:

F = (G * m1 * m2) / r²

Where:

• F is the gravitational force between the two masses (6.67 N).
• G is the gravitational constant (6.6 x 10^-11 Nm²/kg²).
• m1 is the first mass (10²⁴ kg).
• m2 is the second mass (10²⁷ kg).
• r is the distance between the centers of the two masses.

We need to compute r by rearranging the formula:

r² = (G * m1 * m2) / F

Therefore, the distance r is:

r = √((G * m1 * m2) / F)

Substitute the given values into the equation:

r = √((6.6 x 10^-11 Nm²/kg² * 10²⁴ kg * 10²⁷ kg) / 6.67 N)

Calculating inside the square root:

G * m1 * m2 = 6.6 x 10^-11 * 10²⁴ * 10²⁷ = 6.6 x 10⁴⁰ Nm²

Then divide by the force:

6.6 x 10⁴⁰ Nm² / 6.67 N = 0.99 x 10⁴⁰ m²

Finally, calculate the square root:

r = √(0.99 x 10⁴⁰)

r ≈ 1.0 x 10²⁰ m

Therefore, the distance between the two objects is approximately 1.0 x 10²⁰ m.

Antwoorddetails

In order to solve this problem, we can apply **Boyle's Law**, which states that the **pressure** and **volume** of a gas are inversely proportional at a constant temperature. Mathematically, this is expressed as:

P₁V₁ = P₂V₂

Where:

• P₁ is the initial pressure: 105 Nm^-2
• V₁ is the initial volume: 20 m³
• P₂ is the final pressure: 4 x 105 Nm^-2
• V₂ is the final volume, which we need to find

Rearranging the formula to solve for V₂:

V₂ = (P₁V₁) / P₂

Substituting the given values:

V₂ = (105 Nm^-2 x 20 m³) / (4 x 105 Nm^-2)

By calculating:

V₂ = (2100 m³) / 4 x 105

V₂ = 5 m³

Therefore, at a pressure of 4 x 105 Nm^-2, the volume of the gas is 5 m³.

Antwoorddetails

The energy in a moving car is an example of kinetic energy.

To explain simply, **energy** is the ability to do **work** or cause **change**. There are different forms of energy, and **kinetic energy** is one of them. It is defined as the energy possessed by an object due to its motion.

When a car is moving, it possesses **kinetic energy** because its components are in **motion**. This motion energy allows the car to do tasks, such as transporting people or goods from one place to another. The faster the car moves, the greater its **kinetic energy**, and thus it can make a larger impact or do more work.

In contrast, energy forms like **mechanical energy** is a combination of both kinetic and potential energy; **electrical energy** is associated with electrical charge movement, while **potential energy** is related to the position or condition of an object (like a car parked on a hill). Therefore, the specific type of energy from a moving car is **kinetic energy**.

Antwoorddetails

To determine the efficiency of a cell with an internal resistance of 2 Ω while supplying current to a 6 Ω resistor, we can use the concept of power dissipation. Efficiency in this context is the ratio of the power delivered to the external resistor to the total power supplied by the cell. It can be calculated using the formula:

Efficiency (%) = (Power across load resistor / Total power output by cell) × 100

Let's break it down step by step:

• Step 1: Total Resistance - The total resistance in the circuit is the sum of the internal resistance and the resistance of the external resistor:
• Total Resistance (R_total) = Internal Resistance (R_internal) + External Resistance (R_load)
• R_total = 2 Ω + 6 Ω = 8 Ω
• Step 2: Current Calculation - The current flowing through the circuit can be calculated using Ohm's Law, which states V = IR. Assume the electromotive force (EMF) of the cell is E volts:
• Current (I) = E / R_total
• I = E / 8 (Note: We keep E as a variable as it cancels out in the efficiency equation)
• Step 3: Power Delivered to Load - The power delivered to the external resistor can be calculated as:
• Power_load = I² × R_load
• Power_load = (E/8)² × 6
• Step 4: Total Power Supplied by the Cell - The total power supplied by the cell is given by:
• Power_total = EMF × Current = E × (E/8)
• Power_total = E² / 8
• Step 5: Calculate Efficiency: Finally, plug in the power values into the efficiency formula:
• Efficiency (%) = [(E/8)² × 6 / (E² / 8)] × 100
• Simplify to Efficiency (%) = [(6/8)] × 100 = 0.75 × 100 = 75%

The efficiency of the cell when supplying current to a 6 Ω resistor with an internal resistance of 2 Ω is 75%.

Antwoorddetails

The force of attraction between molecules of the same substance is called cohesion.

To understand this simply:

Cohesion refers to the attractive forces acting between similar molecules. For example, water molecules attract each other due to hydrogen bonding, which is a strong intermolecular force.

Let's break down some important concepts:

• Cohesion: This force is responsible for phenomena like water forming droplets and the surface tension that allows some insects to walk on water.
• Capillarity: This is not related to cohesion directly, but rather to the movement of liquid within narrow spaces without the assistance of external forces, usually due to a combination of cohesion and adhesion.
• Adhesion: This is the force of attraction between unlike molecules, such as water sticking to the surface of a glass.
• Surface Tension: While related to cohesion, this specifically refers to the effect caused by cohesive forces at the surface of a liquid, which makes the surface act like a stretched elastic membrane.

In summary, **cohesion** is the force that keeps the molecules of the same substance, like water, attracting each other.

Antwoorddetails

In this problem, the tension in the rope results in a force that acts to pull the body along the horizontal surface. The rope is inclined at 30º to the vertical, which means it makes an angle of 60º with the horizontal since the total angle between vertical and horizontal is 90º.

To find the tension in the rope, we first understand that the component of the tension force acting along the horizontal surface is given by the formula:

F_horizontal = Tension * cos(θ)

Where:

• F_horizontal is the effective force pulling the body along the horizontal, given as 15N.
• Tension is the total tension in the rope that we need to find.
• θ is the angle of inclination with respect to horizontal = 60º (since the rope is 30º to the vertical, it's 60º to the horizontal).

Given that F_horizontal = 15N, we substitute into the equation:

15N = Tension * cos(60º)

We know that cos(60º) = 0.5, therefore:

15N = Tension * 0.5

To find the Tension, divide both sides of the equation by 0.5:

Tension = 15N / 0.5

Tension = 30N

Therefore, the tension in the rope is 30N.

Antwoorddetails

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.

Antwoorddetails

To calculate the acceleration of a charge in an electric field, we start by determining the force acting on the charge. The force \( F \) experienced by a charge \( q \) in a uniform electric field \( E \) is given by the equation:

F = q * E

We are given:

• Charge, q = 1.6 x 10^-19 C
• Electric field, E = 1200 V/m

Substituting these values into the equation for force:

F = 1.6 x 10^-19 C * 1200 V/m

This results in:

F = 1.92 x 10^-16 N

Next, we use Newton’s second law of motion to find the acceleration \( a \) of the charge. This law is given as:

F = m * a

Rearranging for \( a \), we have:

a = F / m

We know:

• Force, F = 1.92 x 10^-16 N
• Mass, m = 9.1 x 10^-31 kg

Substituting these values in the equation for acceleration:

a = \(\frac{1.92 x 10^{-16} N}{9.1 x 10^{-31} kg}\)

Calculating the above expression gives:

a ≈ 2.11 x 10¹⁴ ms^-2

Therefore, the acceleration of the charge is approximately 2.11 x 10¹⁴ ms^-2.

Antwoorddetails

The process you are referring to is called doping. In simple terms, doping is the method of intentionally introducing impurities into an extremely pure semiconductor to change its electrical properties, which increases its conductivity.

Semiconductors, like silicon or germanium, are materials that have electrical conductivity between conductors (like metals) and insulators (like glass). By adding impurities, we can control and enhance their ability to conduct electricity. These impurities are atoms of other elements that either have more or fewer electrons in their outer energy levels compared to those in the semiconductor.

When you add impurities with more electrons, it creates an n-type semiconductor because of the extra *negative* charge carriers (electrons). Conversely, adding impurities with fewer electrons makes a p-type semiconductor, as it creates 'holes' which act as positive charge carriers.

This process of doping is essential for creating various semiconductor devices, like diodes, transistors, and integrated circuits, which are foundational components in all electronic devices. Hence, doping plays a crucial role in the functionality and efficiency of electronic systems.

Antwoorddetails

When selecting the best type of mirror for shaving, the key consideration is how the mirror reflects light and creates an image. For the purpose of shaving, it is important to have a mirror that magnifies the face and provides a clear view.

The best option for a shaving mirror is a concave mirror. Here is why:

• Magnification: A concave mirror curves inward, similar to the inside of a bowl. When you position your face close to a concave mirror, it produces an enlarged image, making it easier to see details while shaving.
• Focusing Light: Concave mirrors can focus light onto a specific point. This provides a bright and clear image, as the reflected light converges at a point in front of the mirror, enhancing visibility.
• Upright Image: When the object (your face) is placed between the mirror and its focal point, the image remains upright and enlarged. This is perfect for detailed activities like shaving.

Other types of mirrors, like convex and plane mirrors, and parabolic mirrors, do not provide the same level of magnification or focused reflecting properties, making them less suitable for shaving purposes.

Antwoorddetails

The part labelled I in the diagram refers to **sunlight**.

Here's a simple explanation:

The given chemical equation is a representation of **photosynthesis**, a process by which green plants, algae, and some bacteria convert light energy, typically from the sun, into chemical energy stored in glucose (C₆H₁₂O₆) and release oxygen (O₂) as a by-product.

In the context of the equation:

- **6CO₂ (Carbon Dioxide) + 6H₂O (Water) → C₆H₁₂O₆ (Glucose) + 6O₂ (Oxygen)**

The arrow indicates the transformation that occurs during the process. The **chlorophyll** (labelled in the diagram) indicates the presence of chlorophyll pigments in the chloroplasts of plant cells which are essential for **absorbing sunlight**.

Since **sunlight** is the source of energy that powers this transformation, it is the correct component for the part labelled I in the diagram.

Antwoorddetails

To understand the concept of resonance in an electrical circuit, it is crucial to know that resonance occurs when the inductive reactance and capacitive reactance are equal in magnitude. This typically happens in a series RLC (Resistor, Inductor, Capacitor) circuit. At resonance, the impedance of the circuit is purely resistive, meaning the circuit behaves as if it only contains a resistor. As a result, the voltages across the inductor and capacitor can be compared at resonance.

In this particular situation, the voltage across the inductor (VL) and the voltage across the capacitor (VC) are of interest due to their roles in resonance:

• At resonance, the inductor and capacitor voltages are equal and opposite. This means that their magnitudes are the same, and they cancel each other out. Therefore, at resonance, VL = VC.

Thus, the correct expression of interest in relation to resonance is VL = VC, which indicates that the voltage across the inductor is equal in magnitude but opposite in phase to the voltage across the capacitor.

Antwoorddetails

The phenomenon of land and sea breeze is primarily attributed to convection.

To understand this, let's first look at what land and sea breezes are:

Land Breeze: At night, the land cools down faster than the sea. The cooler, denser air from the land moves towards the sea, and this is known as a land breeze.

Sea Breeze: During the day, the land heats up more quickly than the sea. The warmer, lighter air over the land rises, and the cooler air from the sea moves in to take its place. This movement of air from the sea to the land is known as a sea breeze.

Both of these processes involve the movement of air due to differences in temperature and density, which is essentially the process of convection.

Convection is the transfer of heat through a fluid (like air or water) and is responsible for moving air masses and creating these breezes. The warm air, being less dense, rises, and the cooler, denser air moves in to replace it.

In contrast, conduction is the transfer of heat through a solid material, and radiation is the transfer of heat in the form of electromagnetic waves, neither of which primarily drive the processes of these breezes, making convection the key player.

Antwoorddetails

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.

Antwoorddetails

apacitance in parallel = one at the top + one under = 2C

The two in the middle are in series = C2 $\frac{C}{2}$

The equivalent capacitance of the capacitors in the circuit above = C2 $\frac{C}{2}$ + 2C = 52 $\frac{5}{2}$C

Antwoorddetails

The gravitational force between two objects is determined by Newton's Law of Universal Gravitation, which can be expressed by the formula:

F = G * (m1 * m2) / r²

where F is the gravitational force, G is the gravitational constant, m1 and m2 are the masses of the objects, and r is the distance between the centers of the two objects.

In this problem, it is given that the initial gravitational force is 10N. According to the formula, the gravitational force is inversely proportional to the square of the distance between the two objects.

So, if the distance between the objects is halved (i.e., r becomes r/2), then the new gravitational force F' can be calculated based on the relationship:

F' = G * (m1 * m2) / (r/2)² = G * (m1 * m2) / (r²/4) = 4 * (G * m1 * m2 / r²) = 4 * F

Since the initial force F was 10N, the new force F' when the distance is halved is:

F' = 4 * 10 = 40N

Thus, the new value of the gravitational force is 40N.