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Pregunta 1 Informe
The energy of light of frequency 2.0 x 1015 Hz is (h = 6.63 x 10−34 Js)
Detalles de la respuesta
To determine the energy of light given its frequency, we can utilize the formula:
E = h × f
Where:
E is the energy of the photon in joules (J)
h is Planck's constant, approximately 6.63 × 10-34 J·s
f is the frequency of light in hertz (Hz)
Given the frequency f = 2.0 × 1015 Hz, we can substitute the known values into our equation:
E = 6.63 × 10-34 J·s × 2.0 × 1015 Hz
To simplify the calculation, multiply the numerical parts and then add the indices of 10:
E = (6.63 × 2.0) × (10-34 × 1015)
E = 13.26 × 10-19 J
This can be approximated to 1.33 × 10-18 J. Thus, the energy of light with the given frequency is 1.33 × 10-18 J.
Pregunta 2 Informe
Which of the following structures enables the exchange of gases in insects?
Detalles de la respuesta
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:
Thus, the correct answer is the tracheae as they specifically enable the exchange of gases in insects.
Pregunta 3 Informe
A wheelbarrow inclined at 60º to the horizontal is pushed with a force of 150N. What is the horizontal component of the applied force
Detalles de la respuesta
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:
Fhorizontal = Fapplied \times \cos(\theta)
Where:
Substitute the values into the formula:
Fhorizontal = 150N \times \cos(60º)
We know that \(\cos(60º)\) equals 0.5.
Therefore:
Fhorizontal = 150N \times 0.5 = 75N
Thus, the **horizontal component** of the applied force is 75N.
Pregunta 4 Informe
The degree of precision of a vernier caliper is
Detalles de la respuesta
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:
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.
Pregunta 5 Informe
The dimension of power is
Detalles de la respuesta
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
Pregunta 6 Informe
Using the diagram above, calculate the relative density of x, if the density of methanol is 800kgm−3
Detalles de la respuesta
density of methanol = 800kgm−3 → 0.8gcm−3
At equilibrium, the density of methanol = the density of liquid x
ρ x h x g = ρ x x hx x g
0.8 x 7.1 = ρ x x 14.2
ρ x = 0.8×7.114.2 = 0.4gcm−3
∴ , the relative density of liquid x = 0.4
Relative density of X = density of liquid xdensity of methanol = 0.40.8 = 0.5
Pregunta 7 Informe
An electron falls from an energy level of -5.44eV to another energy level, E. If the emitted photon is of wavelength 5.68 x 10−6 m, calculate the energy change. [ Plank's constant = 6.63 x 10−34 Js, emitted radiation speed = 3.0 x 108 ms−1 ]
Detalles de la respuesta
To find the energy change when an electron falls from one energy level to another, we need to calculate the energy of the emitted photon. This energy can be found using the formula:
E = hν or E = hc/λ
where:
Substitute these values into the equation:
E = (6.63 x 10-34 Js) * (3.0 x 108 ms-1) / (5.68 x 10-6 m)
First, calculate the numerator:
(6.63 x 10-34) * (3.0 x 108) = 1.989 x 10-25 J·m
Then, divide by the wavelength:
E = 1.989 x 10-25 J·m / 5.68 x 10-6 m = 3.5 x 10-20 J
Therefore, the energy change when the electron falls is approximately 3.5 x 10-20 J.
Checking the options provided, the closest value is 3.49 x 10-20 J.
Pregunta 8 Informe
Which of these gas laws is equivalent to workdone
Detalles de la respuesta
To understand which of these gas laws is equivalent to work done, we must first understand the basic concept of work in the context of gases. For gases, work is done when there is a change in volume under pressure, typically expressed as W = P ΔV, where W is work, P is pressure, and ΔV is the change in volume.
Let's consider the given gas laws:
Among these, Boyle's law relates directly to work done because it involves a change in volume at constant temperature, implying that work occurs as a gas expands or compresses. The equation P₁V₁ = P₂V₂ is foundational for calculating work done in reversible processes, which aligns with the expression for work done on a gas, W = P ΔV. Thus, **Boyle's law** is most directly connected to the concept of work done on a gas.
Pregunta 9 Informe
I
6 X + 6 H2 O → C6 H12 O6 + 6O2
III chlorophyll II IV
Use the diagram above to answer question that follows
The part labelled I is
Detalles de la respuesta
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.
Pregunta 10 Informe
The moon's acceleration due to gravity is 16 of the earth's value. The weight of a bowling ball on the moon would be
Detalles de la respuesta
To determine the weight of a bowling ball on the moon, we need to understand the relationship between weight, gravity, and mass.
Weight is the force exerted by gravity on an object. On Earth, this force depends on the object's mass and the acceleration due to gravity, which is approximately 9.8 m/s². Weight can be calculated using the formula:
Weight = Mass x Gravity
On the moon, the acceleration due to gravity is only 1/6 of Earth’s gravity. This means the gravitational pull on the moon is much weaker compared to the Earth. If we take the Earth's gravity to be 9.8 m/s², the moon's gravity would be:
Moon's Gravity = (9.8 m/s²) x (1/6) ≈ 1.63 m/s²
Given that the weight of an object is directly proportional to the gravitational force, the weight of an object on the moon would be substantially less than its weight on Earth. Thus, the weight of the bowling ball on the moon would be:
Weight on Moon = (Mass) x (1.63 m/s²) = 1/6 of its weight on Earth
Therefore, the weight of a bowling ball on the moon is 1/6 of its weight on Earth.
Pregunta 11 Informe
A medium texture soil with high organic matter is
Detalles de la respuesta
A medium texture soil with high organic matter is best described as loamy soil. Here's why:
Loamy soil is a type of soil that is characterized by a balanced mixture of sand, silt, and clay particles. Because of this blend, loamy soil is not too coarse like sandy soil, nor is it too compact and dense like clay soil, making it a medium texture.
Moreover, loamy soil is renowned for its high organic matter content. This means that it contains a significant amount of decomposed plant and animal residues, which enrich the soil and provide essential nutrients for plant growth. This high organic content enhances the soil's fertility and structure, enabling it to retain moisture yet drain well, making it ideal for farming and gardening.
In conclusion, due to its balanced texture and richness in organic matter, loamy soil is the best fit for a medium-textured soil with high organic matter.
Pregunta 12 Informe
An object is placed 25cm in front of a convex mirror has its image formed 5cm behind the mirror. what is the focal length of the convex mirror
Detalles de la respuesta
Object distance (u) = -25 cm (negative because the object is in front of the mirror)
Image distance (v) = +5 cm (positive because the image is behind the convex mirror)
Using 1f = 1u + 1v
1f = 1−25 + 15
f = 254 = 6.250cm.
Pregunta 13 Informe
The energy stored in the above capacitor is
Detalles de la respuesta
The energy stored in the capacitor = 12 q2C
Where C = 2F, q = 3C
= 12 322 = 94 = 2.25J
Pregunta 14 Informe
Two capacitors of 0.0003μF and 0.0006μF are connected in series, find their combined capacitance.
Detalles de la respuesta
When capacitors are connected in series, the formula to find their combined capacitance \(C_{\text{total}}\) is given by:
\[ \frac{1}{C_{\text{total}}} = \frac{1}{C_1} + \frac{1}{C_2} \]
where \(C_1\) and \(C_2\) are the capacitances of the individual capacitors. In this case, \(C_1 = 0.0003 \, \mu\text{F}\) and \(C_2 = 0.0006 \, \mu\text{F}\).
First, calculate the reciprocal of each capacitance:
\[ \frac{1}{C_1} = \frac{1}{0.0003} \]
\[ \frac{1}{C_2} = \frac{1}{0.0006} \]
Calculating each value:
\[ \frac{1}{0.0003} = \frac{10^6}{3} \] and \[ \frac{1}{0.0006} = \frac{10^6}{6} \]
Now, add these values together:
\[ \frac{1}{C_{\text{total}}} = \frac{10^6}{3} + \frac{10^6}{6} = \frac{10^6 \times 2}{6} + \frac{10^6 \times 1}{6} = \frac{10^6 \times 3}{6} = \frac{10^6}{2} \]
Finally, take the reciprocal of the resulting value to find \(C_{\text{total}}\):
\[ C_{\text{total}} = \frac{2}{10^6} = 0.0002 \, \mu\text{F} \]
So, the combined capacitance of the two capacitors in series is 0.0002 μF.
Pregunta 15 Informe
As per Faraday's laws of electromagnetic induction, an e.m.f is induced in a conductor whenever
Detalles de la respuesta
According to Faraday's laws of electromagnetic induction, an electromotive force (e.m.f) is induced in a conductor whenever it **cuts magnetic flux**. This means that for an e.m.f to be induced, the conductor must move in such a way that it intersects the magnetic lines of force. It is the relative motion between the conductor and the magnetic field that leads to the change in magnetic flux, resulting in the induction of e.m.f.
Let's explore why this is the correct answer using reasoning:
Therefore, the phenomenon where a conductor cuts magnetic flux is essential for electromagnetic induction as per Faraday's laws.
Pregunta 16 Informe
The charge of magnitude 1.6 x 10 −19 C is placed in a uniform electric field of intensity 1200Vm−1 . Calculate its acceleration, if the mass of the charge is 9.1 x 10−31 kg
Detalles de la respuesta
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:
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:
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.
Pregunta 17 Informe
A practical application of total internal reflection is found in
Detalles de la respuesta
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.
Pregunta 18 Informe
The tangential force acting on an object that opposes it from sliding freely on the adjacent surface is called
Detalles de la respuesta
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:
In summary, friction force is the force that acts to oppose sliding between surfaces in contact and acts tangentially, making it the correct answer.
Pregunta 19 Informe
Rainbow is formed when sunlight undergoes
Detalles de la respuesta
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.
Pregunta 20 Informe
The value of R in the above circuit to make the galvanometer measure 2A is
Detalles de la respuesta
Given: Ig = 50mA = 0.05A, I to be measured = 2A, r = 2Ω , Is = I - Ig = 2 - 0.05 = 1.95A
Shunt(R) = IgIs x r
R = 0.051.95 x 10 = 0.2564Ω
Pregunta 21 Informe
Detalles de la respuesta
When you insert a sheet of an insulating material between the plates of an air capacitor, the capacitance will increase.
Here's why:
C = ε₀ * (εr) * (A/d)
Therefore, inserting an insulating material as a dielectric enhances the capacitor's ability to store charge, ultimately resulting in an increase in capacitance.
Pregunta 22 Informe
The mechanical advantage of the machine shown above
Detalles de la respuesta
Mechanical advantage of a machine = LOADEFFORT
In this case of a wedge, we can consider the dimensions given:
Load distance (height of the machine): 15 cm
Effort distance (movement of the effort): 0.5 cm
M.A = 150.5 = 30.0
Pregunta 23 Informe
Electrolysis can be investigated using
Detalles de la respuesta
When investigating electrolysis, the most relevant instrument from the list provided is the Voltameter. This is because the voltameter is specifically designed to measure the amount of substance that is deposited or consumed at electrodes during the electrolysis of an electrolyte. It functions based on the chemical change associated with the electric current passing through the electrolyte.
Here is a simple explanation of how electrolysis works and why a voltameter is useful:
Electrolysis is the process of using electricity to cause a chemical reaction, which is usually a decomposition reaction. This involves passing an electric current through an electrolyte (a substance containing free ions). These ions migrate towards electrodes, resulting in chemical changes. The key aspect to measure during electrolysis is the amount of material (e.g., metal or gas) that is deposited at the electrodes.
The Voltameter helps in understanding electrolysis because:
Voltmeter, Ammeter, and Galvanometer are not used primarily for investigating electrolysis:
Pregunta 24 Informe
The web-feet of frogs and toads is basically for
Detalles de la respuesta
The web-feet of frogs and toads is primarily for swimming. These webbed feet act like paddles, allowing the frog or toad to move efficiently through the water. When the animal spreads its toes, the webbing provides a larger surface area, which gives better propulsion in the water. This adaptation is essential, as many species of frogs and toads spend a significant amount of their time in aquatic environments where efficient swimming helps them in searching for food, escaping predators, and traveling from one place to another. In essence, the webbed feet are a vital feature for their aquatic lifestyle.
Pregunta 25 Informe
The major building block of an organism is...
Detalles de la respuesta
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:
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.
Pregunta 26 Informe
A light ray passing from air into water at an angle of 30º from the normal in air would
Detalles de la respuesta
When light passes from one medium to another, such as from air to water, it bends or refracts. This phenomenon is described by Snell's Law, which states: n₁ * sin(θ₁) = n₂ * sin(θ₂), where:
The refractive index of air is approximately 1, and the refractive index of water is approximately 1.33. Given the angle of incidence in air is 30º:
Using Snell's Law:
1 * sin(30º) = 1.33 * sin(θ₂)
You will find:
sin(θ₂) = sin(30º) / 1.33
sin(θ₂) ≈ 0.5 / 1.33
sin(θ₂) ≈ 0.375
Now, solve for θ₂ by taking the inverse sine (arcsin):
θ₂ ≈ arcsin(0.375)
θ₂ ≈ 22.09º
Thus, when a light ray passes from air into water at an angle of 30º from the normal in air, it will make an angle less than 30º from the normal in water, approximately 22.09º. This is because the light ray bends toward the normal as it enters a denser medium (water).
Pregunta 27 Informe
Pilots uses aneroid barometer to know the height above sea level because
Detalles de la respuesta
Aneroid barometers are compact and lightweight, making them suitable for use in aircraft where space and weight are critical considerations. They provide a reliable measurement of altitude based on changes in atmospheric pressure.
Pregunta 28 Informe
Which of the following operates based on magnetic effect of electric current?
Detalles de la respuesta
The device that operates based on the magnetic effect of electric current is the Dynamo.
To explain further, let's look at the concept of the magnetic effect of electric current:
A Dynamo is a device that converts mechanical energy into electrical energy. It operates based on the phenomenon called electromagnetic induction, which occurs due to the magnetic effect of electric current. When a coil of wire within the dynamo rotates in the presence of a magnetic field, it induces an electric current in the coil. Thus, the operation of a dynamo relies on the interaction between electric current and magnetic fields.
To contrast with other options:
Pregunta 29 Informe
If the S.V.P of water vapour was 13.5mmHg at 33ºC and 7.3mmHg at 7ºC. Find the percentage relative of the air on a day when average air temperature was 33ºC and dew point was 7ºC.
Detalles de la respuesta
To calculate the percentage relative humidity of the air, we use the relationship between the saturation vapour pressure (SVP) and the actual vapour pressure. The formula for relative humidity is:
Relative Humidity (%) = (Actual Vapour Pressure / Saturation Vapour Pressure) * 100
In this problem, the "dew point" refers to the temperature at which air becomes saturated with moisture and water begins to condense. At the dew point, the actual vapour pressure is equal to the saturation vapour pressure at that dew point temperature.
From the problem, we have:
The actual vapour pressure of the air is equal to the SVP at the dew point, which is 7.3 mmHg.
Now we calculate the percentage relative humidity using the formula:
Relative Humidity (%) = (7.3 mmHg / 13.5 mmHg) * 100
Carrying out the calculation:
Relative Humidity (%) = (7.3 / 13.5) * 100 = 0.5407 * 100 = 54.07%
Rounding to the nearest whole number, we get **54%**. Therefore, the percentage relative humidity of the air is 54%.
Pregunta 30 Informe
If the displacement of a car is proportional to the square of time, then the car is moving with
Detalles de la respuesta
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:
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.
Pregunta 31 Informe
The fourth overtone of a closed pipes is 900Hz, its fundamental frequency is
Detalles de la respuesta
To solve this problem, let's first understand how sound works in a closed pipe. A closed pipe has one end closed and another end open. Sound waves inside such a pipe create standing waves, where nodes (points of no movement) and antinodes (points of maximum movement) are formed.
For a closed pipe, the fundamental frequency (also called the first harmonic) has one node at the closed end and one antinode at the open end. The wavelength is four times the length of the pipe.
The overtone sequence for a closed pipe includes only odd harmonics: 1st (fundamental), 3rd, 5th, 7th, etc. The nth overtone is the 2nth + 1 harmonic. The equation for the frequency of a harmonic in a closed pipe is:
f_n = n * f_1, where f_n is the frequency of the nth harmonic and f_1 is the fundamental frequency
In this case, the fourth overtone corresponds to the 9th harmonic because 2 * 4 + 1 = 9. Therefore, we have:
900 Hz = 9 * f_1
To find the fundamental frequency (f_1), we solve for f_1:
f_1 = 900 Hz / 9
f_1 = 100 Hz
Therefore, the fundamental frequency is 100 Hz.
Pregunta 32 Informe
Calculate the upthrust on a spherical ball of volume 4.2 x 10−4 m3 when totally immersed in a liquid of density 1028kgm−3
Detalles de la respuesta
Upthrust(Force) = volume of object x density of liquid x g = V x ρ x g
U = 4.2 x 10−4 x 1028 x 10 ≊ 4.3N
Pregunta 33 Informe
Newton's law of cooling is valid only for a
Detalles de la respuesta
Newton's Law of Cooling states that the rate of heat loss of an object is directly proportional to the difference in temperature between the object and its surroundings, provided that this temperature difference is small.
Therefore, this law is only valid within a small temperature range.
Pregunta 34 Informe
The thermometer whose thermometric property is change in volume with temperature is
Detalles de la respuesta
A thermometer that relies on the **thermometric property** of **change in volume with temperature** is the **Liquid-in-glass thermometer**.
Here is why:
1. **Construction**: A liquid-in-glass thermometer consists of a **glass tube** that encloses a small reservoir filled with a **thermometric liquid**, typically mercury or colored alcohol.
2. **Principle of Operation**: As the **temperature** changes, the **volume of the liquid** inside the tube changes. When the temperature rises, the liquid **expands** and moves up the tube. Conversely, when the temperature decreases, the liquid **contracts** and moves down the tube.
3. **Scale Calibration**: The thermometer has graduations marked along the tube, allowing the user to read the temperature by observing the level of the liquid against these scale markings.
Therefore, the liquid-in-glass thermometer operates on the principle that the **volume of a liquid changes with temperature**, making it the correct answer.
Pregunta 35 Informe
The bursting of water pipes during very cold weather, when the water in the pipes form ice could be attributed to
Detalles de la respuesta
The bursting of water pipes during very cold weather is primarily attributed to the expansion of water on freezing.
Here's why this happens:
1. **Normal water behavior below freezing:** Typically, when most substances freeze, they contract because the molecules get closer together. However, water behaves differently due to its unique molecular structure. As water freezes, it forms a crystalline structure that makes ice less dense than liquid water, causing it to expand.
2. **Effect of expansion:** When water inside a pipe freezes, it expands. This expansion puts tremendous pressure on the pipe walls because the solid ice takes up more space than the liquid water. Most pipes are rigid and do not have enough room to accommodate the expanded volume of ice.
3. **Resulting pressure:** The increased pressure caused by the expanding ice can cause the pipe to crack or burst, especially if there is no other outlet for the water or ice to expand into.
In summary, pipes burst during cold weather primarily due to the expansion of water as it freezes, which creates pressure that the pipe cannot withstand. This phenomenon is due to the unique property of water where it expands upon freezing, unlike most other substances which contract in their solid form.
Pregunta 36 Informe
What is the least possible error encountered when taking measurement with a metre rule?
Detalles de la respuesta
A standard meter rule has markings that are usually every millimeter (1 mm). The least count, which is the smallest measurement that can be accurately read, is often 1 mm.
The least possible error is generally considered to be half of the smallest division, so it is ±0.05cm (or ±0.5mm).
Pregunta 37 Informe
The unit of impedance is
Detalles de la respuesta
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.
Pregunta 38 Informe
Calculate the quantity of heat for copper rod whose thermal capacity is 400Jk−1 for a temperature change of 60ºC to 80ºC
Detalles de la respuesta
To calculate the quantity of heat absorbed or released by a substance, we can use the formula:
Q = C × ΔT
where:
Given:
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.
Pregunta 39 Informe
The part of the inner ear that is responsible for hearing is
Detalles de la respuesta
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:
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.
Pregunta 40 Informe
A body is pulled on a horizontal surface with a rope inclined at 30º to the vertical. If the effective force pulling the body along the horizontal surface is 15N, calculate the tension on the rope.
Detalles de la respuesta
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:
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.
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