19 past paper MCQs on Potential Energy and Absolute Potential Energy, from the Work and Energy unit of MDCAT Physics. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.
1.A 3 kg stone falls from a 20 m high platform. Find its speed at a height of 10 m. (MDCAT 2020)
Correct answer: (b) $14\ \mathrm{m\,s^{-1}}$
It has fallen 10 m, so $v=\sqrt{2gh}=\sqrt{2(10)(10)}\approx14\ \mathrm{m\,s^{-1}}$.
2.A long spring, when stretched by a distance $x$, has potential energy $V$. On increasing the stretching to $nx$, the potential energy of the spring will be: (MDCAT 2022)
Correct answer: (c) $n^2V$
$E=\tfrac{1}{2}kx^2$ goes as the square of the extension.
3.Ignoring friction and the extra forces exerted by the muscles, a pole vault is the conversion of an athlete's running kinetic energy into gravitational potential energy. If an athlete is to lift his body 5 m during a vault, what speed must he have when he plants his pole? (MDCAT 2022)
Correct answer: (b) $10\ \mathrm{m\,s^{-1}}$
$\tfrac{1}{2}mv^2=mgh$ gives $v=\sqrt{2gh}=\sqrt{2(10)(5)}=10\ \mathrm{m\,s^{-1}}$.
4.A fisherman lifts a fish of mass 250 g from rest through a vertical height of 1.8 m. The fish gains a speed of $1.1\ \mathrm{m\,s^{-1}}$. What is the energy gained by the fish? (MDCAT 2023)
Correct answer: (d) 4.6 J
$mgh+\tfrac{1}{2}mv^2=0.25(9.8)(1.8)+\tfrac{1}{2}(0.25)(1.1)^2=4.41+0.15\approx4.6$ J.
5.The work done by the gravitational force on an object as it moves from a reference level to a higher point is (UHS MDCAT 2025)
Correct answer: (b) Always negative
Gravity acts downwards while the body rises, so the force and the displacement are opposed and the work is negative.
6.A 5kg body falls from the height of 30m towards the ground. All its potential energy is converted into heat on impact. What is the heat energy produced? (KMU MDCAT 2025)
Correct answer: (c) 1470J
$mgh=5\times9.8\times30$, which is $1470\,\mathrm{J}$.
7.Potential energy decreases in the process of: (SIBA MDCAT 2025)
Correct answer: (c) Releasing a stretched spring
A stretched spring gives up its stored energy as it returns to its natural length.
8.A diver of mass m is swimming at a depth h below the sea level. If the reference level is taken at sea level, the gravitational potential energy of the diver is: (SIBA MDCAT 2025)
Correct answer: (c) -mgh
The diver is below the reference level, so the potential energy is negative.
9.The escape velocity of a body in the gravitational field of Earth is dependent on: (KMU MDCAT 2024)
Correct answer: (c) Mass of earth
Escape velocity is $\sqrt{2GM/R}$, which carries the mass of the Earth but not that of the body.
10.When dolphin leaves the water it has lots of kinetic energy. At its highest point its energy is: (NUMS MDCAT 2024)
Correct answer: (b) Potential energy
At the top the motion has stopped rising and all the energy is potential.
11.The absolute potential energy is given as Ug = -GmMe/R. The negative sign indicates Earth's gravitational field for mass 'm' is: (NUMS MDCAT 2024)
Correct answer: (c) Attractive
Work must be done against the field to carry the mass away, so the bound state is negative.
12.Ignoring details associated with friction, extra forces exerted by arm and leg muscles, and other factors, we can consider a pole vault as the conversion of an athlete's running kinetic energy to gravitational potential energy. If an athlete is to lift his body 5 m during a vault, what speed must he have when he plants his pole? (UHS MDCAT 2023)
Correct answer: (b) 10 m/s
$\tfrac12mv^2=mgh$ gives $v=\sqrt{2\times10\times5}$, about $10\,\mathrm{m\,s^{-1}}$.
13.According to mechanical energy conservation: (PMC MDCAT 2022)
Correct answer: (c) KE+ PE = constant
With no friction the sum of kinetic and potential energy stays the same.
14.If the water falls from a dam on the turbine wheel 19.6 m below, then the velocity of water at the turbine is: (PMC MDCAT 2022)
Correct answer: (b) 19.6 m/s
$v=\sqrt{2gh}=\sqrt{2\times9.8\times19.6}$, which is $19.6\,\mathrm{m\,s^{-1}}$.
15.The formula to estimate P.E is: (PMC MDCAT 2022)
Correct answer: (b) mgh
The potential energy gained in rising a height $h$ is $mgh$.
16.The amount of work done in moving a body at certain point in a gravitational field to a position of zero potential such that the body is never accelerated is called: (NUMS MDCAT 2022)
Correct answer: (c) Gravitational potential energy
That work is the absolute gravitational potential energy of the body at the point.
17.A body of mass 10 kg is moving at a height of 2 m, with a uniform speed of 2 m/s. (PMC Practice 2021)
Correct answer: (b) 216 J
$mgh+\tfrac12mv^2=10\times9.8\times2+\tfrac12\times10\times4$, that is $216\,\mathrm{J}$.
18.What is the speed of 2.0 kg metallic bob at the mean position of a simple pendulum, when released from its extreme position 0.5m high? (g = 10 ms-2) (PMC MDCAT 2020)
Correct answer: (a) 3.16 ms-1
$v=\sqrt{2gh}=\sqrt{2\times10\times0.5}$, that is $3.16\,\mathrm{m\,s^{-1}}$.
19.Which one of the following force is non-conservative: (PMC MDCAT 2020)
Correct answer: (a) Frictional force
The work done against friction depends on the path taken, so friction is not conservative.