JAMB UTME - Physics - 2018
Question 1 Report
A force of 5N acts at a point Y on a rod XYZ as shown in this diagram. If XYZ is 2m, what is the moment of the force about point X?
Answer Details
To find the moment of the force about point X, we need to first understand what moment is. Moment is the turning effect of a force around a pivot point. It is calculated by multiplying the force by the perpendicular distance between the pivot point and the line of action of the force.
In this case, the force of 5N is acting on the rod at point Y. To find the moment of this force about point X, we need to find the perpendicular distance between point X and the line of action of the force.
From the diagram, we can see that the perpendicular distance between point X and the line of action of the force is 2m (the length of the rod). So, the moment of the force about point X is:
Moment = force x perpendicular distance
= 5N x 2m
= 10Nm
Therefore, the correct answer is: 10Nm.
Question 2 Report
A car traveled at a uniform speed of 100km/h, spends 15m moving from point A to point B along its route. The distance between A and B is
Answer Details
To calculate the distance between point A and point B, we can use the formula:
Distance = Speed x Time
where the speed is given as 100 km/h and the time is given as 15 minutes, which we need to convert to hours.
1 hour = 60 minutes, so 15 minutes = 15/60 hours = 0.25 hours.
Now, we can substitute these values into the formula:
Distance = 100 km/h x 0.25 h = 25 km
Therefore, the distance between point A and point B is 25 km.
is the correct answer.
Question 3 Report
A boy receives the echo of his clap reflected by a nearby hill 0.8s later. If the speed of sound in air is 3.40ms\(^{-1}\), how far is he from the hill?
Answer Details
The speed of sound in air is given as 3.40 m/s. The echo of the clap is heard 0.8 seconds after it was produced, which means it traveled to the hill and back. The time taken for sound to travel to the hill is half of the time taken for it to travel to and from the hill. Therefore, the time taken for sound to travel to the hill is 0.8/2 = 0.4 seconds.
We can use the formula:
distance = speed x time
to calculate the distance between the boy and the hill.
distance = speed of sound x time taken for sound to travel to the hill
distance = 3.40 m/s x 0.4 s
distance = 1.36 m
Therefore, the distance between the boy and the hill is 1.36 meters.
However, the answer options provided are in meters and are significantly larger than 1.36 meters. It is possible that the speed of sound provided in the question is incorrect or the answer options are incorrect.
Question 4 Report
Calculate the effective capacitance of the circuit in the diagram given
Answer Details
The three 2uf capacitors are in parallel to each other so u add them like this
2uf+2uf+2uf=6uf
So u have three capacitors in series
6uf 2uf and 3uf
They are in series so
1/C= 1/6+1/3=1/2
C=2uf
Then the same thing with the last two capay
1/2+1/2=1uf
Thanks
2uf+2uf+2uf=6uf
So u have three capacitors in series
6uf 2uf and 3uf
They are in series so
1/C= 1/6+1/3=1/2
C=2uf
Then the same thing with the last two capay
1/2+1/2=1uf
Thanks
Question 5 Report
In the diagram shown, which of the simple pendulum will resonate with P when set into oscillation?
Answer Details
Question 6 Report
The density of 400cm3 of palm oil was 0.9gcm-3 before frying. If the density of the oil was 0.6gcm-3 after frying, assuming no loss of oil due to spilling, its new volume was?
Answer Details
The density of a substance is defined as its mass per unit volume. Therefore, the mass of the palm oil before frying was:
Mass = Density x Volume = 0.9 g/cm³ x 400 cm³ = 360 g
After frying, the mass of the palm oil remains the same, but its density changes to 0.6 g/cm³. Therefore, the new volume of the palm oil can be calculated by rearranging the density formula:
Volume = Mass / Density = 360 g / 0.6 g/cm³ = 600 cm³
So the new volume of the palm oil after frying is 600 cm³. is the correct answer.
Question 7 Report
What is the resultant resistance of the circuit in the image shown?
Answer Details
Formulae resistance in parallel
= 1/R = 1/R1 +1/R2
1/R = 1/2 +1/2 = 1
Resistance are now in series
R = 1 + 3 + 4
= 8 ohms
= 1/R = 1/R1 +1/R2
1/R = 1/2 +1/2 = 1
Resistance are now in series
R = 1 + 3 + 4
= 8 ohms
Question 8 Report
A beam of light is incident from air to water at an angle of 300. Find the angle of refraction if the refractive index of water is 4/3
Answer Details
X = 43
r = ?
Shell?s law:. 7 = Sin20Sinr0
Vg = Sin300Sinr0
Sinr0 = 3Sin3004
Sin r0 = 0.375
R o = Sin-1 (0.375)
R o = 22.02 o
R o = 22 o
Shell?s law:. 7 = Sin20Sinr0
Vg = Sin300Sinr0
Sinr0 = 3Sin3004
Sin r0 = 0.375
R o = Sin-1 (0.375)
R o = 22.02 o
R o = 22 o
Question 9 Report
The critical angle for light travelling from a transparent medium to air s measured as 340. The refractive index of the medium is
Answer Details
The critical angle is the angle of incidence at which light is just able to pass through the interface between two media and not reflect back. When light travels from a medium with a higher refractive index to a medium with a lower refractive index, it slows down and bends towards the normal. If the angle of incidence is increased, the light will eventually reach a point where it will not be able to escape the higher index medium and will be totally reflected back. This is the critical angle.
The formula for the critical angle can be expressed as follows:
sin(θc) = n2/n1
Where θc is the critical angle, n1 is the refractive index of the first medium, and n2 is the refractive index of the second medium. In this case, the first medium is the transparent medium and the second medium is air, which has a refractive index of approximately 1.
By substituting the value of sin(θc) with the value of 340, and n2 with 1, we can solve for n1.
sin(340) = n1/1
n1 = 1/sin(340)
The value of n1 calculated using this formula is approximately 1.79, which means that the refractive index of the transparent medium is 1.79.
Question 10 Report
The amount of heat needed to raise the temperature of 10kg of Copper by 1K is its
Answer Details
The correct answer is "specific heat capacity."
Specific heat capacity is a measure of how much heat energy is required to raise the temperature of a certain amount of a substance by 1 degree Celsius (or 1 Kelvin, which is the same size as 1 degree Celsius).
In this case, we are dealing with 10kg of copper, so we need to know the specific heat capacity of copper. The specific heat capacity of copper is 0.385 J/g°C (joules per gram per degree Celsius).
To calculate the amount of heat needed to raise the temperature of 10kg of copper by 1K, we need to know the total mass of copper (10kg) and the specific heat capacity of copper (0.385 J/g°C).
The formula for calculating the amount of heat energy required is:
Heat energy = mass x specific heat capacity x change in temperature
Since we want to raise the temperature by 1K, the change in temperature is 1K.
So, the amount of heat energy required to raise the temperature of 10kg of copper by 1K is:
Heat energy = 10kg x 0.385 J/g°C x 1K = 3.85 kJ
Therefore, it takes 3.85 kilojoules (kJ) of heat energy to raise the temperature of 10kg of copper by 1K.
Question 11 Report
The differences observed in solids, liquids and gases may be accounted for by
Answer Details
The differences observed in solids, liquids, and gases can be accounted for by the spacing and forces acting between the molecules.
In a solid, the molecules are packed closely together, so they have a fixed shape and volume. The intermolecular forces are strong enough to keep the molecules in a fixed position relative to one another.
In a liquid, the molecules are still close together, but they are free to move around each other. The intermolecular forces are weaker than in a solid, so the molecules can slide past one another, giving the liquid its ability to flow and take the shape of its container.
In a gas, the molecules are widely spaced and are in constant motion. The intermolecular forces are very weak, so the molecules are free to move around and fill any available space. Gases have no fixed shape or volume.
So, the differences observed in solids, liquids, and gases can be explained by the spacing and forces acting between the molecules. It's not about their relative masses, melting points, or the different molecules in each of them.
Question 12 Report
Natural radioactivity consists of the emission of
Answer Details
Radioactive decay releases different types of energetic emissions. The three most common types of radioactive emissions are alpha particles, beta particles, and gamma rays.
Question 13 Report
Which of the following best describes the energy changes which take place when a steam engine drives a generator which lights a lamp?
Answer Details
The energy changes that take place when a steam engine drives a generator which lights a lamp can be described as:
Heat energy from burning fuel is used to create steam in the boiler of the steam engine. This steam is then used to drive the turbine, which generates kinetic energy as it spins. The kinetic energy is transferred to the generator, which converts it into electrical energy (electricity). The electricity then flows through the wires to the lamp, where it is converted back into light energy, which is what we see.
Therefore, the correct option would be:
Heat ----> Kinetic ----> Electricity ----> Light
Question 14 Report
What effort will a machine of efficiency 90% apply to a load of 180N if its efforts arm is twice as long as its load arm?
Answer Details
Question 15 Report
A lens of focal length 15cm forms on erect image which is three times the size of the object. The distance between the object and the image is ___.
Answer Details
We can use the lens formula, 1/f = 1/v - 1/u, where f is the focal length of the lens, v is the distance between the lens and the image, and u is the distance between the lens and the object.
From the problem, we know that the focal length of the lens is 15 cm, and the image is erect and three times the size of the object. This means that the image distance v is positive and the object distance u is negative (since the object is in front of the lens).
Let's assume that the object distance u is -x cm, where x is a positive number. Then, the image distance v is +3x cm, since the image is three times the size of the object. Substituting these values into the lens formula, we get:
1/15 = 1/(+3x) - 1/(-x)
Simplifying the right-hand side, we get:
1/15 = (1 + 3)/3x
Multiplying both sides by 3x, we get:
3x/15 = 4
Simplifying, we get:
x = 20
Therefore, the distance between the object and the lens is -20 cm (since it is in front of the lens), and the distance between the image and the lens is +60 cm (since it is behind the lens). The distance between the object and the image is the sum of these distances, which is:
(-20) + (+60) = 40 cm
Therefore, the answer is 40cm.
Question 16 Report
In a series R-L-C circuit at resonance, the voltages across the resistor and the inductor are 30V and 40V respectively. What is the voltage across the capacitor?
Answer Details
Question 17 Report
A resistor connected to a 12V battery draws a current of 2A. The energy dispatched in the resistor in 5 minutes is ___.
Answer Details
To calculate the energy dispatched in the resistor, we need to use the formula:
Energy = Power x Time
Where Power is the amount of electrical power consumed by the resistor, and is equal to the product of the voltage across the resistor and the current flowing through it:
Power = Voltage x Current
In this case, the voltage across the resistor is 12V, and the current flowing through it is 2A. Therefore, the power consumed by the resistor is:
Power = 12V x 2A = 24W
Now, we can substitute this value of power along with the given time of 5 minutes into the formula for energy:
Energy = 24W x 5min x 60s/min = 7,200J
Therefore, the energy dispatched in the resistor in 5 minutes is 7,200J.
is the correct answer.
Question 18 Report
A positively charged rod X is brought near an uncharged metal sphere Y and is then touched by a finger with X still in place. When the finger is removed, the result is that Y has
Answer Details
Question 19 Report
The process by which protons are converted into helium atoms with a tremendous release of energy is called?
Answer Details
The process by which protons are converted into helium atoms with a tremendous release of energy is called "thermonuclear fusion".
In this process, two light atomic nuclei combine to form a heavier nucleus, releasing a huge amount of energy in the form of light and heat. This is the same process that powers the sun and other stars. The high temperatures and pressures required for fusion to occur can only be achieved in stars or in controlled environments such as fusion reactors.
Thermonuclear fusion is different from nuclear fission, which is the process of splitting a heavy nucleus into lighter nuclei with the release of energy.
Thermionic emission and photoelectric emission are different processes that involve the emission of electrons from a material due to heating or exposure to light, respectively.
Question 20 Report
When a known standard resistor of 2.0 is connected to the 0.0cm end of a meter bridge, the balance point is found to be at 55.0cm. What is the value of the unknown resistor?
Answer Details
A meter bridge is an instrument used to measure the unknown resistance of a conductor. The meter bridge consists of a long resistance wire AB of uniform cross-sectional area and a battery of known voltage connected across its ends. A galvanometer is connected across a point C on the wire, which is called the null point or balance point.
When a known standard resistor of 2.0 ohms is connected to the 0.0cm end of the meter bridge wire, the balance point is found to be at 55.0cm. This means that the resistance of the unknown resistor is equal to the resistance of a portion of the meter bridge wire between the 0.0cm and the 55.0cm point.
To find the value of the unknown resistor, we can use the principle of the Wheatstone bridge, which states that the ratio of the resistances in the two arms of a balanced bridge is equal.
Let R be the resistance of the unknown resistor, then we have:
R/2.0 = (100 - 55.0)/55.0
Simplifying this expression, we get:
R = 2.0 x (100 - 55.0)/55.0
R = 1.64 ohms
Therefore, the value of the unknown resistor is 1.64 ohms.
Question 21 Report
A body of mass 100g moving with a velocity if 10ms-1 collides with a wall. If after collision it moves with a velocity of 2.0ms−1 in the opposite direction, calculate the change in momentum.
Answer Details
Momentum = Mass x Velocity
Change in Momentum = Mass x (change in velocity)
Change in Momentum = Mass x (v - u)
Mass = 100g = 0.1kg
U = 2ms−1
V = 10ms−1
Change in momentum = m (v − u)
= 0.1 (10 − 2)
= 0.1 (8)
= 0.8Ns
Change in Momentum = Mass x (change in velocity)
Change in Momentum = Mass x (v - u)
Mass = 100g = 0.1kg
U = 2ms−1
V = 10ms−1
Change in momentum = m (v − u)
= 0.1 (10 − 2)
= 0.1 (8)
= 0.8Ns
Question 22 Report
The electrochemical equivalent of silver is 0.0012g/C. If 36.0g of silver is to be deposited by electrolysis on a surface by passing a steady current for 5mins, the current must be?
Answer Details
The electrochemical equivalent of silver is a measure of the amount of silver that is deposited on a surface per unit of charge. In this case, the electrochemical equivalent of silver is 0.0012 grams per Coulomb of charge. To deposit 36.0 grams of silver by electrolysis, we need to know the amount of charge that must be passed through the solution.
The amount of charge is given by:
Q = m/z
where m is the mass of silver to be deposited, 0.0012 is the electrochemical equivalent of silver, and z is the charge on one mole of electrons (z = 1 for a single electron).
So, the amount of charge required is:
Q = 36.0 g / 0.0012 g/C = 30000 C
The current, I, is given by:
I = Q / t
where t is the time for which the current is flowing. In this case, t = 5 minutes.
So, the current required is:
I = 30000 C / (5 x 60 s) = 100 A
Therefore, the current must be 100 Amperes.
Question 23 Report
An object weighs 30N in air and 21N in water. The weight of the object when completely immersed in a liquid of relative density 1.4 is
Answer Details
Weight of water displaced = upthrust = 30 - 21 = 9N
Mass of water displaced = 910
= 0.9kg
Volume of object = 9 × 10−4
m3
= (9 × 10−4
) (1.4 ×103)
= 1.26kg = 12N
30 - 12.6 = 17.4N
Question 24 Report
If the fraction of the atoms of a radioactive material left after 120years is \( \frac{1}{64} \), what is the half-life of the material? \( \frac{1}{64} \)
Answer Details
The half-life of a radioactive material is the time it takes for half of the atoms in a sample to decay. The fraction of atoms left after a certain number of half-lives can be calculated using the formula:
fraction left = (1/2)^(number of half-lives)
Let's use this formula to solve the problem. We know that the fraction of atoms left after 120 years is 1/64, which means that:
(1/2)^(number of half-lives) = 1/64
To solve for the number of half-lives, we can take the logarithm of both sides:
log[(1/2)^(number of half-lives)] = log(1/64)
Using the rule that log(a^b) = b*log(a), we can simplify the left side of the equation:
number of half-lives * log(1/2) = log(1/64)
Dividing both sides by log(1/2), we get:
number of half-lives = log(1/64) / log(1/2)
Using a calculator or the change of base formula, we can evaluate this expression:
number of half-lives = 6
Therefore, the half-life of the material is 120/6 = 20 years.
Question 25 Report
Which of the following is not a product of nuclear fusion?
Answer Details
Neutron is not a product of nuclear fusion. Nuclear fusion is the process by which two or more atomic nuclei come together to form a heavier nucleus, releasing a large amount of energy in the process. In most fusion reactions, the resulting products are alpha particles (helium nuclei) and energy in the form of gamma rays.
X-rays and gamma rays are both forms of high-energy electromagnetic radiation that can be produced by nuclear reactions, including nuclear fusion. Alpha particles are also a common product of nuclear fusion, especially in the fusion reactions that power the sun.
However, neutrons are not typically produced in fusion reactions. In fact, one of the major challenges in developing fusion as a practical energy source is finding ways to produce and control the high-energy neutrons that are generated in the process. Neutrons can be produced in some types of fusion reactions, but they are not a primary product.
In summary, neutron is not a product of nuclear fusion, while X-rays, Y-rays (assuming this is a valid form of radiation), and alpha particles are common products of this process.
Question 26 Report
A 20kg mass is to be pulled up a slope inclined at 300 to the horizontal. If efficiency of the plane is 75%. The force required to pull the load up the plane is J [g=10ms\(^{-2}\)]
Answer Details
The force required to pull a 20kg mass up a slope inclined at 300 can be calculated using the formula:
force = mass * gravity * sin(angle)
where mass is 20kg, gravity is 10 m/s^2 and angle is 300.
The formula for efficiency is:
efficiency = output force / input force
where output force is the force required to pull the mass up the slope and input force is the force applied to the rope.
Since the efficiency of the plane is 75%, the input force is 4 times the output force.
So, the output force can be calculated as:
output force = input force / 4
input force = mass * gravity * sin(angle) / efficiency
input force = 20 * 10 * sin(300) / 0.75
input force = 533.2 N
And the output force can be calculated as:
output force = input force / 4
output force = 533.2 / 4
output force = 133.3 N
So, the force required to pull the load up the plane is 133.3 N.
Question 27 Report
A room is heated by means of a charcoal fire, an occupants of the room standing away from the fire is warmed mainly by
Answer Details
The main way that the occupants of a room standing away from a charcoal fire are warmed is by radiation. Radiation is the transfer of heat energy through electromagnetic waves, and it can travel through empty space.
In this scenario, the charcoal fire emits radiation in the form of infrared waves, which travel through the air and warm up the objects (including the occupants) in the room. Convection, on the other hand, is the transfer of heat through the movement of fluids (such as air), but in this case, the air in the room is not being actively circulated by a fan or other mechanism. Conduction involves the transfer of heat through direct contact between two objects, but the occupants are not in direct contact with the fire. Reflection refers to the bouncing of radiation off a surface, but it is not a significant factor in this scenario as most of the radiation is absorbed by the objects in the room.
Question 28 Report
Which of the following is true of an electrical charge?
Answer Details
The correct answer is option D: "All of the above."
An electrical charge refers to the presence of an excess or deficit of electrons in an atom or molecule. In this context, positive charge means a deficit of electrons, whereas negative charge means an excess of electrons. Electric current refers to the flow of charged particles, typically electrons, through a conductor. Therefore, an electric current means the movement of electrons.
In summary, all of the given options are true of an electrical charge, and they all relate to the behavior of electrons in an electrically charged system.
Question 29 Report
Water of mass 150g at \(60^\circ\)c is added to 300g of water at \(20^\circ\)c and the mixture is well stirred. Calculate the temperature of the mixture.(neglect heat losses to the surroundings)
Answer Details
To solve this problem, we can use the principle of conservation of energy, which states that energy cannot be created or destroyed, only transferred or converted from one form to another. In this case, the energy transferred is in the form of heat.
We can use the formula:
Q = m*c*(ΔT)
where Q is the heat transferred, m is the mass of the water, c is the specific heat capacity of water, and ΔT is the change in temperature.
First, we can calculate the heat transferred from the hot water to the cold water:
Q1 = 150g * 4.18 J/(g°C) * (60°C - T)
Q1 = 627 * (60 - T)
where T is the temperature of the mixture.
Next, we can calculate the heat transferred from the cold water to reach the final temperature of the mixture:
Q2 = 300g * 4.18 J/(g°C) * (T - 20°C)
Q2 = 1254 * (T - 20)
Since the heat transferred between the two water samples must be equal, we can set Q1 equal to Q2 and solve for T:
627 * (60 - T) = 1254 * (T - 20)
37620 - 627T = 1254T - 25080
1881T = 62760
T = 33.4°C
Therefore, the temperature of the mixture is approximately 33°C.
Answer: 33°C
Question 30 Report
What type of reaction is represented by the following scheme?
\( {}_{1}^{2}X + {}_{1}^{2}Y \longrightarrow {}_{2}^{3}Z + {}_{1}^{0}n + \text{energy} \)
Answer Details
The type of reaction represented by the given scheme is a nuclear fission reaction.
Nuclear fission is a process where a heavy nucleus is split into smaller nuclei with the release of energy. In the given scheme, a heavy element X is split into two lighter elements, Y and Z, along with the release of energy and some neutrons (n).
In a nuclear fission reaction, a neutron is usually absorbed by the nucleus of the heavy element, which then becomes unstable and splits into two smaller nuclei and some neutrons. These neutrons can then go on to split other heavy nuclei, resulting in a chain reaction.
In the given scheme, the release of energy and the presence of neutrons suggest that it is a fission reaction. Moreover, the scheme depicts the process of splitting a heavy element into two lighter elements, which is a characteristic of a fission reaction.
Therefore, the type of reaction represented by the given scheme is a nuclear fission reaction.
Question 31 Report
In the diagram given if the atmospheric pressure is 760mm, the pressure in the chamber G Is
Answer Details
Question 32 Report
In the diagram given the hanging mass m2 is adjusted until m1 is on the verge of sliding. The coefficient of static
Answer Details
I think the correct option is C (m2m1
). The coefficient of friction is a ratio of two forces and hence g will cancel out.
Question 33 Report
Electrical power is transmitted at a high voltage rather than a low voltage because the amount of energy loss is due to
Answer Details
The primary reason that power is transmitted at high voltages is to increase efficiency. As electricity is transmitted over long distances, there are inherent energy losses along the way. High voltage transmission minimizes the amount of power lost as electricity flows from one location to the next. How? The higher the voltage, the lower the current. The lower the current, the lower the resistance losses in the conductors. And when resistance losses are low, energy losses are low also. Electrical engineers consider factors such as the power being transmitted and the distance required for transmission when determining the optimal transmission voltage
Question 34 Report
A ball of mass 5.0kg hits a smooth vertical wall normally with a speed of \(2\text{ms}^{-1}\). Determine the magnitude of the resulting impulse
Answer Details
The magnitude of the resulting impulse can be calculated using the formula impulse = change in momentum. In this scenario, the ball experiences a change in velocity (speed) as it hits the wall. The ball's initial momentum is equal to its mass times its velocity, and its final momentum is zero since it comes to a stop after hitting the wall. The change in momentum is equal to the final momentum minus the initial momentum, which is equal to the negative of the initial momentum.
Since the ball has a mass of 5.0 kg and a velocity of 2 m/s, its initial momentum is 5.0 kg * 2 m/s = 10.0 kg m/s. Therefore, the change in momentum is -10.0 kg m/s and the magnitude of the resulting impulse is 10.0 kg m/s, which is equal to 10.0 Ns.
So, the correct answer is 10.0kgms−1.
Question 35 Report
The inner diameter of a small test tube can be measured accurately using a
Answer Details
A vernier caliper is a measuring device used to precisely measure linear dimensions. It is a very useful tool to use when measuring the diameter of a round objects like cylinders because the measuring jaws can be secured on either side of the circumference.
Vernier calipers have both a fixed main scale and a moving vernier scale. The main scale is graduated in either millimetres or tenths of an inch. The vernier scale allows much more precise readings to be taken (usually to the nearest 0.02mm or 0.001 inch) in comparison to a standard ruler (which only measures to th nearest 1mm or 0.25 inch).
The vernier scale was invented by French mathematician Pierre Vernier in 1631. As part of the vernier caliper, it is used together with the main scale, and helps to provide very precise measurements. Vernier calipers usually show either imperial or metric measurements, but some measure in both.
Vernier calipers have both a fixed main scale and a moving vernier scale. The main scale is graduated in either millimetres or tenths of an inch. The vernier scale allows much more precise readings to be taken (usually to the nearest 0.02mm or 0.001 inch) in comparison to a standard ruler (which only measures to th nearest 1mm or 0.25 inch).
The vernier scale was invented by French mathematician Pierre Vernier in 1631. As part of the vernier caliper, it is used together with the main scale, and helps to provide very precise measurements. Vernier calipers usually show either imperial or metric measurements, but some measure in both.
Question 36 Report
The friction which exist between two layers of liquid in relative motion is called
Answer Details
The correct answer is "Viscosity". Viscosity is the property of a fluid that describes its resistance to flow. When two layers of liquid are in relative motion, the viscosity of the liquid causes friction between the layers. This friction creates a resistance to the movement of one layer past the other. The greater the viscosity of the liquid, the greater the friction and the more difficult it is for the layers to move past each other. This property is important in many industrial and natural processes, such as the flow of oil in pipelines or the movement of blood through the human body.
Question 37 Report
A man walks 1km due east and then 1 km due north. His displacement is
Answer Details
The man first walks 1 km due east, which means he has moved 1 km horizontally to the right of his starting point. Then, he walks 1 km due north, which means he has moved 1 km vertically upwards from his previous position. To find his displacement, we need to draw a straight line from his starting point to his final position, which represents the shortest distance between the two points. This line is called the displacement vector. We can use the Pythagorean theorem to calculate the length of the displacement vector. The horizontal and vertical distances are the two legs of a right-angled triangle, and the hypotenuse is the length of the displacement vector. Using the Pythagorean theorem, we get: displacement = √((1 km)^2 + (1 km)^2) = √2 km The direction of the displacement vector is the angle between the displacement vector and the due north direction. We can find this angle using trigonometry. The tangent of the angle is the ratio of the horizontal distance to the vertical distance: tan(θ) = (1 km) / (1 km) = 1 Using a calculator, we can find that the angle is 45°. Therefore, the man's displacement is √2 km in the direction N 45° E. So, the correct answer is √2km N 45°E.
Question 38 Report
Which of the following has the lowest internal resistance when new?
Answer Details
Among the given options, the Accumulator has the lowest internal resistance when new.
Internal resistance is the resistance that a battery or cell provides to the flow of electric current within itself. Lower internal resistance means that the battery can supply more current to an external circuit without losing much of its own energy as heat.
An Accumulator, also known as a rechargeable battery, is designed to be charged and discharged multiple times. It has a relatively low internal resistance when new, meaning it can provide a higher current than the other cells listed while wasting less energy internally as heat.
A Leclanche cell and Daniell cell are primary cells, meaning they are designed to be used once and discarded. They have higher internal resistance compared to the accumulator, which limits their ability to supply high currents.
A Torch battery, also known as a dry cell, is also a primary cell and has a higher internal resistance than the accumulator. It is commonly used in small electronic devices and has a longer shelf life than Leclanche and Daniell cells.
In summary, an Accumulator has the lowest internal resistance when new, which makes it an ideal choice for applications requiring high current delivery such as electric vehicles, power tools, and renewable energy systems.
Question 39 Report
Temperature is the property of a body which is proportional to the ____.
Answer Details
Temperature is proportional to the average kinetic energy of the molecules in a body. This means that as the average kinetic energy of the molecules increases, so does the temperature.
Think about it like this: the hotter an object, the more energy its molecules have. This energy is what makes the molecules move faster, and therefore, the temperature of the object increases.
The average kinetic energy of the molecules is a better measure of temperature than the maximum speed of the molecules because temperature is a measure of the overall energy distribution, not just the energy of a single molecule.
Question 40 Report
The time rate of loss of heat by a body is proportional to the
Answer Details
The correct answer is "difference in temperature between the body and its surroundings."
When a body is at a higher temperature than its surroundings, it will lose heat to the surroundings until it reaches thermal equilibrium, i.e., until the temperatures of the body and its surroundings are equal. The rate at which the body loses heat is proportional to the temperature difference between the body and its surroundings. This is known as Newton's law of cooling.
The law of cooling applies to a wide range of situations, from the cooling of hot beverages to the cooling of electronic devices. It is important to understand this law because it allows us to predict how long it will take for a body to cool down to a certain temperature, and to design systems that can regulate the temperature of a body, such as heaters or refrigerators.
