A force F = (2î + 3ĵ) N acts on a body moving with velocity v = (4î − ĵ) m/s. What power does the force deliver?
Correct answer A. 5 W
Topic / 30 questions
Work and Energy MCQs
Work and Energy MCQs cover work done by a force, kinetic and gravitational potential energy, absolute potential energy, power and the efficiency of practical machines. They help MDCAT, ECAT and FSc candidates practise both definitions and short calculations, and every question on MCQs360 shows its correct answer instantly.
- Electromagnetic Induction 30
- Fluid Dynamics 30
- Electrostatics 30
- Electronics 30
- Electromagnetism 30
- Current Electricity 30
- Work and Energy 30
- Waves 30
- Vectors and Equilibrium 30
- Nuclear Physics 30
- Dawn of Modern Physics 30
- Thermodynamics 30
- Rotational and Circular Motion 30
- Atomic Spectra 30
- Alternating Current 30
- Force and Motion 30
A water pump with an input power of 2 kW and an efficiency of 70% raises water through 10 m. Taking g = 9.8 m/s², what mass of water does it lift each second?
Correct answer C. 14.3 kg
A 2 kg block sliding at 6 m/s on a rough horizontal surface comes to rest. How much work does friction do on the block?
Correct answer B. −36 J
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Taking g = 9.8 m/s² at the surface and Earth’s radius R = 6.4 × 10⁶ m, what is the absolute gravitational potential energy of a 1 kg mass on the Earth’s surface?
Correct answer A. −6.27 × 10⁷ J
A stone is dropped from a height of 20 m. Ignoring air resistance and taking g = 9.8 m/s², what is its speed just before hitting the ground?
Correct answer A. 19.8 m/s
A 10 kg crate is pushed 5 m across a floor with coefficient of kinetic friction 0.3. Taking g = 9.8 m/s², how much energy is dissipated as heat by friction?
Correct answer B. 147 J
An electric motor takes 800 W of electrical power and delivers 600 W of mechanical power. What is its efficiency?
Correct answer A. 75%
A car’s engine provides a driving force of 2000 N while the car moves at a steady 25 m/s. What power does the engine deliver?
Correct answer D. 50 kW
A stone falls freely under gravity with no air resistance. Which statement is correct?
Correct answer D. The sum of its kinetic and potential energies stays constant
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A crane lifts a 500 kg load through 12 m in 20 s at steady speed. Taking g = 9.8 m/s², what is its output power?
Correct answer B. 2940 W
A 5 kg box is lifted vertically through 4 m. Taking g = 9.8 m/s², how much gravitational potential energy does it gain?
Correct answer D. 196 J
What is the kinetic energy of a 2 kg ball moving at 3 m/s?
Correct answer C. 9 J
A force of 50 N pulls a trolley 10 m along the floor while acting at 60° to the direction of motion. How much work does it do?
Correct answer C. 250 J
Which statement about conservative forces is correct?
Correct answer A. The work done by them is independent of the path taken
A porter carries a box on his head and walks along a level road at constant velocity. How much work does he do on the box against gravity?
Correct answer C. Zero
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Two bodies have the same momentum but different masses. Which has the greater kinetic energy?
Correct answer A. The lighter body
According to the work-energy principle, the net work done on a body equals ____
Correct answer C. the change in its kinetic energy
Why is the efficiency of a practical machine always less than 100%?
Correct answer A. Some input energy is lost as heat, sound and other forms
A box is pushed at constant speed along a rough floor. What becomes of the work done against friction?
Correct answer C. It is dissipated as heat
The kilowatt-hour (kWh) is a unit of which quantity?
Correct answer D. Energy
About Work and Energy MCQs
Questions in this unit ask you to calculate work done by a force acting at an angle to the displacement, decide when work is positive, zero or negative, and find the work done by friction as a body slows down. Energy questions cover kinetic energy, gravitational potential energy near the Earth's surface and absolute potential energy measured from infinity. Others treat power as the dot product of force and velocity, the work-energy principle, the heat produced by work against friction, and why real machines always have an efficiency below 100%.
Key facts to remember
- Work done: W = F·d = Fd cos θ; it is negative when θ is greater than 90°.
- Kinetic energy K.E. = ½mv², and gravitational potential energy near the Earth is P.E. = mgh.
- Absolute gravitational potential energy is U = −GMm/r, taken as zero at infinity.
- Power P = W/t = F·v; its SI unit is the watt (1 W = 1 J s⁻¹).
- Work-energy principle: the net work done on a body equals its change in kinetic energy.
- Efficiency = (useful output energy ÷ total input energy) × 100%, always less than 100% in practice.
Exams that include Work and Energy MCQs
Pakistan
- MDCAT
- ECAT (UET)
- NUMS
- AKU
- FSc boards
India
- NEET
- JEE Main
Bangladesh
- HSC
- Medical Admission Test
How to prepare for Work and Energy MCQs
- Always check the angle between force and displacement; only the component along the displacement does work.
- For a body brought to rest by friction, the work done by friction equals minus its initial kinetic energy.
- Learn why absolute potential energy is negative: work must be done to take a body from that point to infinity.
- Practise P = F·v with vectors in î, ĵ form, as this is a favourite MDCAT calculation.
Frequently asked questions
Which exams ask Work and Energy MCQs?
Work and Energy is part of the FSc physics syllabus, so its MCQs appear in MDCAT, ECAT (UET), NUMS and AKU entry tests and in FSc board papers. Students in India meet the same ideas in NEET and JEE Main, and Bangladeshi students in HSC and the medical admission test.
Why is absolute potential energy negative?
Absolute gravitational potential energy is measured from infinity, where it is taken as zero. Gravity is attractive, so work must be done on a body to move it from any point to infinity. Its energy at that point is therefore less than zero, given by U = −GMm/r.
Last reviewed October 2026