100 High-Scoring MCQs on Work and Energy (Set - 2) | Class 11 Physics | Unit 5

100 High-Scoring MCQs (Set-2) on Work and Energy, Unit-5, Class 11 Physics (Unit-Wise Practice)

This post contains 100 carefully selected multiple-choice questions (MCQs) from Unit-5: Work and Energy of Class 11 Physics, designed strictly according to the FBISE syllabus. These MCQs include a well-balanced mix of numerical and conceptual problems, making them exam-ready, revision-friendly, and high-scoring.

Whether you are preparing for annual board exams, chapter tests, or competitive entry tests, this collection thoroughly covers all the key concepts and formulas of Work and Energy, helping students master the chapter with confidence.

This unit-wise MCQ set includes questions from:

• Definition and concept of Work and Energy

• Work done by a constant and variable force

• Kinetic energy (KE) and potential energy (PE)

• Work-Energy theorem

• Power and its calculation

• Conservation of mechanical energy

• Elastic and inelastic collisions

• Gravitational and spring potential energy

• Impulse and momentum

• Numerical applications combining work, energy, and motion

• Real-life applications of energy concepts in mechanics

Each MCQ is provided with the correct answer and a clear, concise explanation, helping students strengthen concepts, avoid common mistakes, and solve numerical problems confidently.

Prepare smartly, revise efficiently, and boost your exam score in Unit-5: Work and Energy with these 100 high-yield MCQs.

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MCQ 1

A net force of 4 N acts horizontally on a body (Vi = 0) of mass 2 kg for 6 s. Its kinetic energy will be:

a. 12 J
b. 144 J
c. 72 J
d. 48 J

Correct Answer: b. 144 J

Explanation:
Impulse = $F \Delta t = 6 \times 4 = 24$Ns → Δp = 24 kg·m/s
$K\mathrm{.}E=\frac{p^2}{2m}=\frac{{24}^2}{2\times 2}=144\text{J}$

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MCQ 2

Work done by a force is zero if the angle between force and displacement is:

a. 0°
b. 45°
c. 90°
d. 180°

Correct Answer: c. 90°

Explanation:
$W = F s \cos\theta$.
At $\theta = 90^\circ$, $\cos {90}^{\circ }=\mathrm{0,\; so\; work\; done\; is\; zero.}$

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MCQ 3

A body moving in a circular path does no work because:

a. Force is zero
b. Speed is constant
c. Force is perpendicular to displacement
d. Mass is constant

Correct Answer: c. Force is perpendicular to displacement

Explanation:
Centripetal force is always perpendicular to displacement, hence work done is zero.

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MCQ 4

The SI unit of work is equivalent to:

a. N/m
b. kg m² s⁻²
c. kg m s⁻¹
d. N s

Correct Answer: b. kg m² s⁻²

Explanation:
$1\,\text{J} = 1\,\text{N·m} = 1\,\text{kg m}^2 \text{s}^{-2}$

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MCQ 5

A 1000 N force is exerted on a body which moves with constant velocity for a distance of 200 m. Work done will be:

a. Zero
b. 1000 N
c. 2000 J
d. None

Correct Answer: a. Zero

Explanation:
Constant velocity → net force = 0 → W = F_net × S = 0

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MCQ 6

If a body of mass 100 kg is lifted through a vertical height of 100 m, the work done (kJ) will be:

a. 980 kJ
b. 98 kJ
c. 0.98 kJ
d. 980 × 10³ kJ

Correct Answer: b. 98 kJ

Explanation:
W = P.E = m g h = 100 × 9.8 × 100 = 98000 J = 98 kJ

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MCQ 7

The dot product of force and velocity is:

a. Power
b. Work
c. Impulse
d. Momentum

Correct Answer: a. Power

Explanation:
P = F · v

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MCQ 8

If work is done at the rate of 2000 J/s, its power is:

a. 2 W
b. 2 kW
c. 2 MW
d. 200 W

Correct Answer: b. 2 kW

Explanation:
P = W/t = 2000 J / 1 s = 2000 W = 2 kW

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MCQ 9

One horsepower is equal to:

a. 550 W
b. 550 kW
c. 746 W
d. None

Correct Answer: c. 746 W

Explanation:
1 hp = 746 W

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MCQ 10

Negative work is done when the angle between F and S is:

a. θ < 90°
b. 90° < θ ≤ 180°
c. 180° < θ < 270°
d. Both b & c

Correct Answer: b. 90° < θ ≤ 180°

Explanation:
W = F S cos θ → negative when cos θ < 0 → 90° < θ ≤ 180°

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MCQ 11

The light and heavy bodies have equal K.E. Which one has greater momentum?

a. Both equal
b. Light body
c. Heavy body
d. Impossible to say

Correct Answer: b. Light body

Explanation:
p = √(2 m K) → smaller mass → larger speed → larger momentum

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MCQ 12

An object of mass 1 g is whirled in a horizontal circle of radius 0.5 m at constant speed 2 m/s. The work done by tension during one revolution is:

a. Zero
b. 1 J
c. 2 J
d. 4 J

Correct Answer: a. Zero

Explanation:
W = F · S cos 90° = 0 (tension is perpendicular to displacement)

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MCQ 13

1 kg mass has K.E of 1 J. Its speed is:

a. 1 m/s
b. 4.4 m/s
c. 1.4 m/s
d. 2.5 m/s

Correct Answer: c. 1.4 m/s

Explanation:
K.E = ½ m v² → v = √(2 × 1 / 1) ≈ 1.414 m/s

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MCQ 14

Two bodies with K.E ratio 4:1 and equal momentum. The ratio of masses is:

a. 1:4
b. 4:1
c. 1:2
d. 1:1

Correct Answer: a. 1:4

Explanation:
p constant → K.E = p² / 2m → larger K.E → smaller mass

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MCQ 15

Work done by centripetal force on an object is:

a. Zero
b. Positive
c. Negative
d. All

Correct Answer: a. Zero

Explanation:
Centripetal force is perpendicular to motion → W = F·S cos 90° = 0

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MCQ 16

Work done by conservative force along a closed path is:

a. Zero
b. Maximum
c. Positive

Correct Answer: a. Zero

Explanation:
By definition, work along closed path = 0 for conservative forces.

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MCQ 17

A 500 N force is applied on a body at 60° to +X-axis and moves 100 m along X-axis. Work done:

a. Zero
b. 25 KJ
c. 433.01 J
d. None

Correct Answer: c. 433.01 J

Explanation:
W = F S cos θ = 50 × 10 × cos60° = 25,000 J = 25 KJ

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MCQ 18

When a falling object of mass m moves with terminal velocity, the work done by gravity is:

a. Zero
b. Negative
c. m g h
d. None

Correct Answer: a. Zero

Explanation:
At terminal velocity → net force = 0 → W = 0

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MCQ 19

The work done by gravity on a pendulum is:

a. Positive
b. Negative
c. Zero
d. None

Correct Answer: c. Zero

Explanation:
Gravity does zero net work over one complete oscillation.

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MCQ 20

One erg =

a. 1 g·cm²·s⁻²
b. 1 g·cm·s⁻²
c. 1 g·m²·s⁻¹
d. 1 g·cm²·s

Correct Answer: a. 1 g·cm²·s⁻²

Explanation:
By definition, 1 erg = 1 g·cm²·s⁻²

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MCQ 21

Which object has greater K.E?

a. Mass 3M, velocity V
b. Mass 2M, velocity V/3
c. Mass 3M, velocity V/2
d. Mass M, velocity 4V

Correct Answer: d. Mass M, velocity 4V

Explanation:
K.E = ½ m v² → highest value for largest v²

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MCQ 22

1 erg =

a. 1 dyne·cm
b. 10⁷ J
c. 10⁴ kJ
d. 10⁻⁷ J

Correct Answer: d. 10⁻⁷ J

Explanation:
Conversion: 1 erg = 10⁻⁷ J

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MCQ 23

Kinetic energy of a body depends upon:

a. Velocity only
b. Mass only
c. Mass and velocity
d. Force

Correct Answer: c. Mass and velocity

Explanation:
$K = \frac{1}{2} mv^2$

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MCQ 24

One mega watt-hour =

a. 36 × 10⁶ J
b. 36 × 10¹² J
c. 36 × 10⁹ J
d. 36 × 10⁸ J

Correct Answer: d. 36 × 10⁸ J

Explanation:
1 MWh = 10⁶ W × 3600 s = 3.6 × 10⁹ J (≈36 × 10⁸ J)

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MCQ 25

Input energy = 1000 J, output = 100 J sound + 300 J heat. Efficiency:

a. 60%
b. 70%
c. 40%
d. 100%

Correct Answer: a. 60%

Explanation:
Useful work = 1000 – (100 + 300) = 600 J
η = 600 / 1000 × 100 = 60%

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MCQ 26

If momentum increases by 20%, K.E increases by:

a. 44%
b. 36%
c. 44% decrease
d. 36% decrease

Correct Answer: a. 44%

Explanation:
ΔK.E% ≈ 2n + n²/100 → 2(20) + 400/100 = 44%

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MCQ 27

Two objects with same momentum, A has more K.E than B if its mass is:

a. More than A
b. Less than A
c. Moving faster than A
d. Moving slower than A

Correct Answer: b. Less than A

Explanation:
K.E = p² / 2m → smaller mass → higher K.E

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MCQ 28

The SI unit of work is equivalent to:

a. N/m
b. kg m² s⁻²
c. kg m s⁻¹
d. N s

Correct Answer: b. kg m² s⁻²

Explanation:
$1\,\text{J} = 1\,\text{N·m} = 1\,\text{kg m}^2 \text{s}^{-2}$

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MCQ 29

Kinetic energy of a body depends upon:

a. Velocity only
b. Mass only
c. Mass and velocity
d. Force

Correct Answer: c. Mass and velocity

Explanation:
$K = \frac{1}{2} mv^2$

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MCQ 30

Unit of power in British engineering system:

a. Watt
b. kW
c. Horsepower
d. Joule

Correct Answer: c. Horsepower

Explanation:

Horsepower is the traditional British unit of power.

1 Horsepower = 746 W

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MCQ 31

Potential energy of a body at height h depends upon:

a. Mass only
b. Height only
c. Gravity only
d. Mass, height, and gravity

Correct Answer: d. Mass, height, and gravity

Explanation:
$PE=mg\mathrm{h }$

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MCQ 32

Work is negative when F and d are:

a. Parallel
b. Anti-parallel
c. Perpendicular
d. None

Correct Answer: b. Anti-parallel

Explanation:
W = F·d cos θ → θ = 180° → W negative

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MCQ 33

Rate of doing work in any instant is called:

a. Average power
b. Variable power
c. Constant power
d. Instantaneous power

Correct Answer: d. Instantaneous power

Explanation:
P_inst = dW/dt

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MCQ 34

Efficiency of fluorescent lamp:

a. 20%
b. 30%
c. 40%
d. 100%

Correct Answer: b. 30%

Explanation:
Memory-based from textbook

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MCQ 35

Velocity of 1 kg mass with K.E = 1 J:

a. 2 m/s
b. 1/√2 m/s
c. 4 m/s
d. √2 m/s

Correct Answer: d. √2 m/s

Explanation:
v = √(2 K/m) = √2 ≈ 1.414 m/s

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MCQ 36

A body freely falling under gravity has:

a. Constant PE
b. Constant KE
c. Increasing KE and decreasing PE
d. Decreasing KE and increasing PE

Correct Answer: c. Increasing KE and decreasing PE

Explanation:
As height decreases, PE converts into KE.

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MCQ 37

The law of conservation of energy states that energy:

a. Can be created
b. Can be destroyed
c. Can be transformed
d. Can be lost

Correct Answer: c. Can be transformed

Explanation:
Energy cannot be created or destroyed, only transformed from one form to another.

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MCQ 38

Which of the following is a conservative force?

a. Friction
b. Air resistance
c. Gravity
d. Viscosity

Correct Answer: c. Gravity

Explanation:
Work done by conservative forces is path-independent.

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MCQ 39

Critical velocity of satellite:

a. √(2 g R)
b. √(g R)
c. g R /2
d. None

Correct Answer: b. √(g R)

Explanation:
Derived from centripetal and gravitational force: v = √(g R)

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MCQ 40

Missile fired at 98 m/s, θ = 30° with horizontal. Airborne distance:

a. 196 m
b. 122.5 m
c. 98 m
d. 2940 m

Correct Answer: b. 122.5 m

Explanation:
Time in air: t = 2 V sinθ / g → y_max etc.

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MCQ 41

The work done by friction is always:

a. Positive
b. Zero
c. Negative
d. Maximum

Correct Answer: c. Negative

Explanation:
Friction always opposes motion, so work done is negative.

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MCQ 42

Angle of projection for which range = maximum height:

a. tan⁻¹ 1/4
b. tan⁻¹ 4
c. tan⁻¹ 1/2
d. tan⁻¹ 2

Correct Answer: b. tan⁻¹ 4

Explanation:
R = H → derived from projectile motion equations

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MCQ 43

If velocity-time graph is a straight line parallel to time-axis, then:

a. Acceleration is constant
b. Acceleration is zero
c. Acceleration is variable
d. Velocity is zero

Correct Answer: b. Acceleration is zero

Explanation:
Slope = acceleration → horizontal line → slope = 0

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MCQ 44

Two blocks of masses 10 kg and 3 kg placed in contact, acted by 40 N. Acceleration of 1 kg mass:

a. 40 m/s²
b. 10 m/s²
c. 30 m/s²
d. 50 m/s²

Correct Answer: b. 10 m/s²

Explanation:
a = F / (m1 + m2) = 40 / (10 + 3) ≈ 10 m/s²

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MCQ 45

Mechanical energy is the sum of:

a. Kinetic and thermal energy
b. Potential and thermal energy
c. Kinetic and potential energy
d. Heat and work

Correct Answer: c. Kinetic and potential energy

Explanation:
Mechanical Energy = KE + PE

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MCQ 46

In an isolated system, total mechanical energy remains:

a. Zero
b. Constant
c. Maximum
d. Minimum

Correct Answer: b. Constant

Explanation:
No external force → energy conservation holds.

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MCQ 47

Power is defined as:

a. Work × time
b. Work ÷ time
c. Force × distance
d. Energy × velocity

Correct Answer: b. Work ÷ time

Explanation:
$P = \frac{W}{t}$

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MCQ 48

Time required for projectile to reach max height H:

a. √(8 H/g)
b. √(4 H/g)
c. √(2 H/g)
d. √(H/g)

Correct Answer: c. √(2 H/g)

Explanation:
t = V sinθ / g → using H = (V sinθ)² / 2g → t = √(2H/g)

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MCQ 49

Two cars moving opposite directions: 10 m/s and 5 m/s. Relative velocity:

a. 5 m/s
b. -5 m/s
c. 10 m/s
d. 15 m/s

Correct Answer: d. 15 m/s

Explanation:
Opposite directions → add velocities → 10 + 5 = 15 m/s

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MCQ 50

Two bodies move in same direction; distance increases at 4 m/s, opposite 6 m/s. Speeds of bodies:

a. 5 m/s, 1 m/s
b. 6 m/s, 1 m/s
c. 3 m/s, 3 m/s
d. 4 m/s, 2 m/s

Correct Answer: a. 5 m/s, 1 m/s

Explanation:
v1 + v2 = 6, v1 - v2 = 4 → solve → v1 = 5 m/s, v2 = 1 m/s

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MCQ 51

The SI unit of power is:

a. Joule
b. Newton
c. Watt
d. Pascal

Correct Answer: c. Watt

Explanation:
$1\,\text{W} = 1\,\text{J s}^{-1}$

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MCQ 52

A machine is said to be ideal if its efficiency is:

a. 50%
b. Less than 100%
c. Greater than 100%
d. 100%

Correct Answer: d. 100%

Explanation:
Ideal machine has no energy loss.

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MCQ 53

Rocket motion in space obeys conservation of:

a. Energy
b. Charge
c. Mass
d. Momentum

Correct Answer: d. Momentum

Explanation:
No external force → linear momentum conserved

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MCQ 54

Quantities constant in collision:

a. Momentum, K.E, Temp
b. Momentum, K.E
c. Momentum, Temp
d. Momentum only

Correct Answer: d. Momentum only

Explanation:
Momentum conserved; K.E only in elastic collision

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MCQ 55

Fireman slides down rope with breaking strength ¾ W. Minimum acceleration:

a. 3/4 g
b. 1/2 g
c. 1/4 g
d. Zero

Correct Answer: c. 1/4 g

Explanation:
F = W - T → a = (1/4) g

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MCQ 56

Force on a 2 N mass with momentum change 120 kg·m/s:

a. 8 s
b. 30 s
c. 60 s
d. 120 s

Correct Answer: c. 60 s

Explanation:
F = ΔP/Δt → Δt = ΔP/F = 120/2 = 60 s

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MCQ 57

Efficiency of a machine is the ratio of:

a. Output work to input work
b. Input work to output work
c. Power to energy
d. Force to velocity

Correct Answer: a. Output work to input work

Explanation:
$\eta = \frac{\text{Useful output}}{\text{Input}}$

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MCQ 58

Force by wall on water hitting at 10 m/s, volume flow 0.0001 m³/s:

a. 1 N
b. 10 N
c. 100 N
d. None

Correct Answer: a. 1 N

Explanation:
F = Δp/Δt = ρ V ΔV = 1 N

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MCQ 59

Which quantity remains conserved in elastic collision?

a. Kinetic energy only
b. Momentum only
c. Both kinetic energy and momentum
d. Potential energy

Correct Answer: c. Both kinetic energy and momentum

Explanation:
Elastic collisions conserve both KE and momentum.

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MCQ 60

Angle between centripetal force and momentum in circular motion:

a. 90°
b. 0°
c. 180°
d. 30°

Correct Answer: a. 90°

Explanation:
Centripetal force perpendicular to velocity → θ = 90°

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MCQ 61

If the velocity of a body is doubled, its kinetic energy becomes:

a. Double
b. Half
c. Four times
d. Same

Correct Answer: c. Four times

Explanation:
KE ∝ $v^2$

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MCQ 62

Kinetic energy of a body depends upon:

a. Velocity only
b. Mass only
c. Mass and velocity
d. Acceleration

Correct Answer: c. Mass and velocity

Explanation:
$KE = \frac{1}{2}mv^2$

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MCQ 63

Gravitational potential energy depends upon:

a. Velocity
b. Acceleration
c. Height
d. Time

Correct Answer: c. Height

Explanation:
$PE = mgh$

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MCQ 64

Cricket ball hit at 45°, K.E = E. K.E at highest point:

a. 0
b. E/2
c. E/√2
d. E

Correct Answer: b. E/2

Explanation:
Horizontal component of velocity remains → K.E = ½ E

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MCQ 65

Spring potential energy is given by:

a. $\frac{1}{2}kx$
b. $kx^2$
c. $\frac{1}{2}kx^2$
d. $kx$

Correct Answer: c. $\frac{1}{2}kx^2$

Explanation:
Energy stored in a stretched/compressed spring.

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MCQ 66

The work–energy theorem states that work done equals change in:

a. Momentum
b. Power
c. Energy
d. Velocity

Correct Answer: c. Energy

Explanation:
Work done = change in kinetic energy.

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MCQ 67

A shell mass m moving with velocity V breaks into 2 pieces. Velocity of larger piece:

a. V
b. 2V
c. 4V/3
d. 3V/4

Correct Answer: c. 4V/3

Explanation:
Conservation of momentum

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MCQ 68

Rubber ball dropped 5 m, rises 1.8 m. Velocity lost factor:

a. 16/25
b. 2/5
c. 3/5
d. 9/25

Correct Answer: c. 3/5

Explanation:
V₂ / V₁ = √(h₂ / h₁) = √(1.8 / 5) → V₂ / V₁ = 3/5

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MCQ 69

Person travels x = 20t + 2A t². Acceleration:

a. A / 4
b. 4 / A
c. 4
d. 4A

Correct Answer: d. 4A

Explanation:
x = ut + ½ a t² → compare → a = 4A

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MCQ 70

A body of mass 2 kg moving with speed 3 m/s has kinetic energy:

a. 3 J
b. 6 J
c. 9 J
d. 18 J

Correct Answer: d. 18 J

Explanation:
$K = \frac{1}{2}mv^2 = \frac{1}{2}×2×9 = 18\,\text{J}$

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MCQs No. 71

If no net work is done on a body, its kinetic energy will:

a. Increase
b. Decrease
c. Remain unchanged
d. Become zero

Correct Answer: c. Remain unchanged

Explanation:
According to the work–energy theorem,

$$W = \Delta KE$$

If work done is zero, change in kinetic energy is zero.

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MCQs No. 72

The work done by gravitational force on a body moving horizontally is:

a. Maximum
b. Minimum
c. Zero
d. Infinite

Correct Answer: c. Zero

Explanation:
Gravitational force acts vertically while displacement is horizontal, so

$$W = F s \cos 90^\circ = 0$$

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MCQs No. 73

A body of mass 2 kg has velocity 3 m/s. Its kinetic energy is:

a. 3 J
b. 6 J
c. 9 J
d. 18 J

Correct Answer: c. 9 J

Explanation:

$$KE = \frac{1}{2}mv^2 = \frac{1}{2}(2)(3^2)=9\,J$$

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MCQs No. 74

Which force is conservative in nature?

a. Frictional force
b. Air resistance
c. Gravitational force
d. Viscous force

Correct Answer: c. Gravitational force

Explanation:
Work done by gravitational force is path-independent, hence conservative.

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MCQs No. 75

The area under a power–time graph represents:

a. Force
b. Momentum
c. Work done
d. Velocity

Correct Answer: c. Work done

Explanation:

$$\text{Work} = \int P \, dt$$

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MCQs No. 76

In absence of non-conservative forces, the quantity conserved is:

a. Kinetic energy only
b. Potential energy only
c. Mechanical energy
d. Momentum

Correct Answer: c. Mechanical energy

Explanation:

$$KE + PE = \text{constant}$$

when no energy loss occurs.

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MCQs No. 77

The potential energy stored in a stretched spring depends upon:

a. Extension only
b. Force only
c. Square of extension
d. Mass attached

Correct Answer: c. Square of extension

Explanation:

$$PE = \frac{1}{2}kx^2$$

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MCQs No. 78

When a ball strikes the ground and rebounds with less speed, the collision is:

a. Elastic
b. Perfectly elastic
c. Inelastic
d. Perfectly inelastic

Correct Answer: c. Inelastic

Explanation:
Some kinetic energy is lost during collision, hence inelastic.

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MCQs No. 79

Power of a machine is measured as:

a. Work done per unit time
b. Force per unit time
c. Energy per unit distance
d. Momentum per unit time

Correct Answer: a. Work done per unit time

Explanation:

$$P = \frac{W}{t}$$

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MCQs No. 80

If velocity of a body is doubled, its kinetic energy becomes:

a. Doubled
b. Four times
c. Half
d. Eight times

Correct Answer: b. Four times

Explanation:

$$KE \propto v^2$$

So doubling velocity increases KE by $2^2 = 4$ times.

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MCQ 81

Bullet mass m, velocity V fired into block M. Velocity of system:

a. m/(M+m) V
b. (M+m)/m V
c. m/(M+m) V
d. M/(M-m) V

Correct Answer: a. m/(M+m) V

Explanation:
Conservation of momentum

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MCQ 82

Conservation of linear momentum ≡

a. Newton 1st Law
b. Newton 2nd Law
c. Newton 3rd Law
d. None

Correct Answer: a. Newton 1st Law

Explanation:
No net force → momentum constant

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MCQ 83

Elastic head-on collision, same mass, initially at rest. Velocity of first particle after collision:

a. 2V
b. -V
c. V
d. 0

Correct Answer: d. 0

Explanation:
v1 = (m1 - m2)/(m1 + m2) V1 + … = 0

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MCQ 84

In an inelastic collision:

a. KE increases
b. KE decreases
c. KE remains same
d. Momentum is not conserved

Correct Answer: b. KE decreases

Explanation:
Some energy converts into heat/sound.

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MCQ 85

Bomb dropped from plane at 200 mph, reaches ground in 5 s. Altitude:

a. 4 miles
b. 122.5 m
c. 40 m
d. 10 m

Correct Answer: b. 122.5 m

Explanation:
H = ½ g t² = ½ × 9.8 × 25 ≈ 122.5 m

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MCQ 86

In an elastic collision:

a. Momentum only is conserved
b. Energy only is conserved
c. Both KE and momentum are conserved
d. Neither is conserved

Correct Answer: c. Both KE and momentum are conserved

Explanation:
Elastic collision conserves total mechanical energy.

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MCQ 87

Change in momentum requires:

a. Force applied
b. Change in time
c. Change in distance
d. Change in temperature

Correct Answer: a. Force applied

Explanation:
Δp/Δt = F

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MCQ 88

Mechanical energy is conserved when:

a. Friction acts
b. Only conservative forces act
c. Acceleration is zero
d. Momentum is constant

Correct Answer: b. Only conservative forces act

Explanation:
Non-conservative forces cause energy loss.

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MCQ 89

SI unit of power is:

a. Joule
b. Watt
c. Newton
d. Pascal

Correct Answer: b. Watt

Explanation:
$P = \frac{W}{t}$

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MCQ 90

Does not change when force applied:

a. Mass
b. Velocity
c. Position
d. Acceleration

Correct Answer: a. Mass

Explanation:
Mass is invariant

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MCQ 91

Impulse same unit as:

a. Force
b. Energy
c. Momentum
d. None

Correct Answer: c. Momentum

Explanation:
Impulse = Δp → unit = kg·m/s

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MCQ 92

Horizontal component of velocity in projectile motion:

a. Increase
b. Decrease
c. Constant
d. None

Correct Answer: c. Constant

Explanation:
No horizontal force → Vx constant

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MCQ 93

Projectile travels 1000 m. Max height:

a. 400 m
b. 800 m
c. 500 m
d. 250 m

Correct Answer: d. 250 m

Explanation:
H = R/4 for 45° projection

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MCQ 94

Impulse is equal to change in:

a. Energy
b. Velocity
c. Momentum
d. Force

Correct Answer: c. Momentum

Explanation:
$I = \Delta p$

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MCQ 95

A body of mass 2 kg moving at 3 m/s has kinetic energy:

a. 3 J
b. 6 J
c. 9 J
d. 18 J

Correct Answer: c. 9 J

Explanation:
$KE = \frac{1}{2}mv^2 = \frac{1}{2}(2)(9) = 9J$ 

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MCQ 96

Work done by gravity on a freely falling body is:

a. Zero
b. Negative
c. Positive
d. Variable

Correct Answer: c. Positive

Explanation:
Force and displacement are in same direction.

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MCQ 97

If no work is done on a body, then its:

a. Velocity must change
b. Energy must change
c. KE remains constant
d. Momentum becomes zero

Correct Answer: c. KE remains constant

Explanation:
No work → no change in KE.

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MCQ 98

A machine with efficiency 80% loses energy mainly due to:

a. Momentum
b. Friction
c. Weight
d. Pressure

Correct Answer: b. Friction

Explanation:
Energy dissipates as heat due to friction.

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MCQ 99

Area under force–displacement graph represents:

a. Power
b. Momentum
c. Work
d. Energy loss

Correct Answer: c. Work

Explanation:
Work = area under F–s curve.

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MCQ 100

Why are brakes applied slowly in vehicles?

a. To increase power
b. To reduce impulse
c. To increase KE
d. To conserve energy

Correct Answer: b. To reduce impulse

Explanation:
Increasing stopping time reduces force.