Work, Energy and PowerNEET MCQs with solutions
Work, Energy and Power covers work done by constant and variable forces, kinetic and potential energy, work-energy theorem, conservation of energy, power and collisions (elastic and inelastic). NEET tests energy conservation problems, work-energy theorem application and collision calculations.
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- 11 Physics
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- 515 questions
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Practise 24 questions
Tap an option to check it. Questions from every NCERT topic in this chapter, from easy to hard.
Q1Work
Which of the following is the correct SI unit of work?
Not quite — the answer is B.
Work = Force × displacement (along force direction), so its SI unit is N·m = joule (J). Watt is the unit of power; Newton is the unit of force; Pascal is the unit of pressure.
Q2Work
A force of 20 N acts on a body causing a displacement of 5 m in the same direction. The work done is:
Not quite — the answer is C.
Work = Fd cosθ = 20 × 5 × cos0° = 100 J. Since force and displacement are parallel, θ = 0° and cos0° = 1. Dividing instead of multiplying gives the trap value 4 J.
Q3Potential Energy
Gravitational potential energy of a body of mass m at a height h above the Earth's surface (near the surface) is given by:
Not quite — the answer is A.
Near Earth's surface, gravitational PE is U = mgh with reference at ground level. Option B incorrectly introduces a factor of ½. Options C and D are dimensionally incorrect.
Q4Potential Energy
A body of mass 5 kg is raised vertically through 8 m. Take g = 10 m/s². The increase in its gravitational potential energy is:
Not quite — the answer is B.
ΔU = mgh = 5 × 10 × 8 = 400 J. Option A halves the height (uses 4 m). Option C doubles the height. Option D omits mass entirely from the calculation.
Q5Centre of Mass & Collision Applications
The centre of mass of a uniform rod lies at:
Not quite — the answer is A.
For a uniform rod, mass is evenly distributed, so the COM lies at the midpoint — its geometric centre. Non-uniform rods have COM shifted toward the heavier side. This result follows directly from xCM = Σmx/Σm applied to a continuous uniform body.
Q6Centre of Mass & Collision Applications
Two particles of masses 2 kg and 3 kg are at x = 0 m and x = 10 m. The x-coordinate of their COM is:
Not quite — the answer is B.
xCM = (2×0 + 3×10)/5 = 30/5 = 6 m. Option C (5 m) is the unweighted average — valid only when masses are equal. The heavier 3 kg mass pulls the COM closer to x = 10 m.
Q7Collision
A collision in which both momentum and kinetic energy are conserved is called:
Not quite — the answer is A.
In an elastic collision both linear momentum and kinetic energy are conserved. In inelastic collisions, momentum is conserved but KE is not. Oblique refers to geometry of impact, not energy classification.
Q8Collision
Two bodies stick together after a collision and move as one combined mass. This type of collision is called:
Not quite — the answer is B.
Bodies sticking together and moving with a common velocity is the defining characteristic of a perfectly inelastic collision. KE loss is maximum in this case. In elastic collisions bodies separate; in partially inelastic they separate but with some KE loss.
Q9Conservation of Mechanical Energy
A ball is dropped from a height h. Neglecting air resistance, which quantity remains constant throughout its motion?
Not quite — the answer is A.
Only gravity (conservative force) acts, so total mechanical energy KE + PE remains constant. During the fall, PE decreases while KE increases by an equal amount. Momentum is not conserved — gravity provides an external impulse.
Q10Conservation of Mechanical Energy
A body of mass 2 kg falls freely from a height of 20 m. Take g = 10 m/s². Its total mechanical energy during the motion is:
Not quite — the answer is B.
Initial ME = PE = mgh = 2 × 10 × 20 = 400 J. Only gravity acts so ME is conserved — it remains 400 J at every point during the fall. Option A halves mgh by forgetting to multiply correctly. Option C doubles the correct answer.
Q11Power
The SI unit of power is:
Not quite — the answer is A.
Power is rate of doing work; its SI unit is Watt (W), defined as 1 joule per second. Joule is unit of energy, Newton of force, Pascal of pressure.
Q12Power
A machine does 2400 J of work in 30 s. Its average power is:
Not quite — the answer is B.
Average power P = W/t = 2400/30 = 80 W. Common error is multiplying W × t instead of dividing, or using wrong time units.
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Get RankUp on Google PlayQ13Grand Test
A 4 kg block slides down a smooth incline from a vertical height of 5 m. The speed of the block at the bottom is: (g = 10 m/s²)
Not quite — the answer is B.
By conservation of energy: mgh = ½mv², so v = √(2gh) = √(2×10×5) = 10 m/s. Mass cancels — result is mass-independent. Option A uses v = √(gh), missing the factor of 2 from ½mv².
Q14Grand Test
A spring of spring constant 500 N/m is compressed by 0.2 m. The elastic potential energy stored is:
Not quite — the answer is C.
Elastic PE = ½kx² = ½×500×(0.04) = 10 J. Option A (20 J) arises from forgetting the ½ factor, giving kx² = 20 J. Option B (100 J) is the force kx = 100 N, not energy.
Q15Work-Energy Theorem
The work-energy theorem states that the net work done on a body is equal to:
Not quite — the answer is A.
W_net = ΔKE — net work by all forces equals change in KE. Option B describes energy conservation (ΔKE = −ΔPE), not the theorem. Option D (momentum change) equals impulse (F×t), not work (F×s).
Q16Work-Energy Theorem
A net force of 20 N acts on a block causing it to move 5 m in the direction of force, starting from rest. The increase in kinetic energy is:
Not quite — the answer is B.
W_net = F × s = 20 × 5 = 100 J. By WET, ΔKE = W_net = 100 J. Option A (50 J) computes ½ × F × s, incorrectly applying a ½ factor to work. Option D (200 J) doubles F × s without physical basis.
Q17Conservative & Non-Conservative Forces
A force F acts on a particle. Which condition confirms that F is a conservative force?
Not quite — the answer is A.
A conservative force is defined by path-independence: its work depends only on the endpoints, not the route. A force being positive, constant, or aligned with motion are not defining criteria. Friction can be constant in magnitude yet remains non-conservative.
Q18Conservative & Non-Conservative Forces
A particle travels from A to B under gravity, taking a winding path three times longer than the straight-line distance. Compared to the straight-line path, the work done by gravity along the winding path is:
Not quite — the answer is B.
Gravity is conservative — work depends only on the vertical displacement between A and B, not path length. Since endpoints are identical, work done by gravity is the same on both paths. Option A is the classic proportionality error. Option D confuses non-straight paths with zero work.
Q19Kinetic Energy
The kinetic energy of a body of mass m moving with speed v is given by:
Not quite — the answer is A.
KE = ½mv² by definition, derived from work done accelerating a body from rest. Option B omits the factor ½. Option C uses incorrect factor 2. Option D has units of kg·m/s (momentum), not joules — dimensionally wrong.
Q20Kinetic Energy
A body of mass 4 kg moves with a speed of 5 m/s. Its kinetic energy is:
Not quite — the answer is C.
KE = ½mv² = ½ × 4 × 25 = 50 J. Option D (100 J) omits the factor ½, computing 4 × 25 directly. Option A (25 J) computes ½ × 5² without multiplying by mass. Option B (20 J) uses KE = ½mv (speed not squared), giving ½ × 4 × 5 = 10... corrected trap: ½ × 4 × 5 = 10 is not 20 — see note.
Q21Potential Energy Curve
A graph of potential energy U versus position x has a minimum at x = 4 m and the curve is smooth on both sides. The nature of equilibrium at x = 4 m and the force on a particle placed exactly there are:
Not quite — the answer is A.
At a PE minimum, dU/dx = 0 so F = 0 and d²U/dx² > 0 confirms stable equilibrium. Any displacement increases PE and the restoring force returns the particle. Options C and D incorrectly describe force at an equilibrium point.
Q22Potential Energy Curve
The potential energy curve of a particle has a smooth maximum at x = 2 m. The nature of equilibrium at this point and the force on the particle placed exactly there are:
Not quite — the answer is B.
At a PE maximum, dU/dx = 0 so force is zero and equilibrium exists. Since d²U/dx² < 0, any displacement lowers PE and pushes the particle further away — unstable equilibrium. Option D incorrectly denies equilibrium at a PE maximum.
Q23Work
A particle moves horizontally while a constant vertical force acts downward on it. The work done by the vertical force on the particle is:
Not quite — the answer is A.
When force is perpendicular to displacement, θ = 90° and cos90° = 0, so W = Fd cos90° = 0. The vertical force has no component along horizontal displacement. Multiplying magnitudes directly without cosθ is the common error.
Q24Work
A particle moves 4 m east under a force of 8 N directed eastward. The work done is:
Not quite — the answer is D.
Work = Fd cosθ = 8 × 4 × cos0° = 32 J. Force and displacement are in the same direction so θ = 0°. Dividing F by d gives the trap value 2, and adding gives 12 — both common errors.
ELITE question · AIR under 50 level
This chapter has 163 ELITE questions for students aiming at the very top. They are only in the app.
Unlock ELITE questions in the appKey Energy Concepts
Quick revision: most questions in this chapter test these facts.
| Concept | Key Formula / Fact |
|---|---|
| Work | W = F·d·cosθ; positive if θ < 90°; zero if θ = 90°; negative if θ > 90° |
| KE | KE = ½mv²; work-energy theorem: W_net = ΔKE |
| PE (spring) | PE = ½kx²; restoring force F = −kx (Hooke's law) |
| Conservation | KE + PE = constant (no non-conservative forces) |
| Power | P = W/t = F·v; SI unit: watt (W) |
| Elastic collision | Both momentum and KE conserved; in 1D with equal masses: velocities exchange |
What the app covers in this chapter
515 questions in total, each with a detailed explanation.
| Work | 80 |
| Potential Energy | 60 |
| Centre of Mass & Collision Applications | 57 |
| Collision | 55 |
| Conservation of Mechanical Energy | 40 |
| Power | 39 |
| Grand Test | 38 |
| Work-Energy Theorem | 37 |
| Conservative & Non-Conservative Forces | 37 |
| Kinetic Energy | 36 |
| Potential Energy Curve | 36 |
Questions students ask
Is Work, Energy and Power important for NEET?
Yes — energy conservation, work-energy theorem and collision problems are tested every year. Both conceptual and numerical questions appear.
Which topics should I revise first?
Master work done by various forces, the work-energy theorem, energy conservation on inclines and springs, power calculations, and elastic vs inelastic collision formulas.
How many questions from this chapter are on RankUp?
The RankUp app has 515 questions on Work, Energy and Power, including 163 ELITE questions. Every question has a detailed explanation.
