Mock Test – JEE Main – Physics- Work Energy and Power

Q1.

A force of 10 N acts on a body moving 5 m in the direction of the force. Work done:

A) 50 J
B) 15 J
C) 5 J
D) 10 J

Q2.

Kinetic energy of a body is 100 J. Mass = 2 kg. Speed of body:

A) 10 m/s
B) 5 m/s
C) 15 m/s
D) 20 m/s

Q3.

Potential energy of a body of mass 3 kg at height 5 m (g = 10 m/s²):

A) 50 J
B) 150 J
C) 15 J
D) 100 J

Q4.

Work done by gravity on a freely falling body is:

A) Zero
B) Equal to change in kinetic energy
C) Negative
D) Equal to potential energy

Q5.

Work done by a force along perpendicular displacement:

A) Maximum
B) Zero
C) Negative
D) Equal to potential energy

Q6.

A body of mass 4 kg moves with velocity 3 m/s. Its kinetic energy:

A) 18 J
B) 12 J
C) 9 J
D) 36 J

Q7.

Power is defined as:

A) Work × Time
B) Work / Time
C) Force × Time
D) Energy × Velocity

Q8.

A constant force F moves a body from rest to velocity v. Work done:

A) $\frac{1}{2} m v^2$ 21mv2
B) $m v$ mv
C) $F v$ Fv
D) $m v^2$ mv2

Q9.

Work-energy theorem states:

A) Work done = Change in potential energy
B) Work done = Change in kinetic energy
C) Power = Work / Time
D) Work done = Force × Distance

Q10.

A body moving in circular path at constant speed. Work done by centripetal force:

A) Positive
B) Negative
C) Zero
D) Equal to kinetic energy

Q11.

Potential energy of a spring stretched by x:

A) $\frac{1}{2} k x$ 21kx
B) $k x$ kx
C) $\frac{1}{2} k x^2$ 21kx2
D) $k x^2$ kx2

Q12.

If total mechanical energy is conserved, the force acting is:

A) Non-conservative
B) Conservative
C) Friction
D) Variable

Q13.

A body of mass 2 kg falls from height 5 m. Velocity on reaching ground (ignore air resistance):

A) 5 m/s
B) 10 m/s
C) 15 m/s
D) 20 m/s

Q14.

Instantaneous power delivered by a force F moving body at velocity v:

A) F / v
B) F × v
C) F × t
D) F × d

Q15.

Work done by a body moving in closed path under conservative force:

A) Positive
B) Negative
C) Zero
D) Depends on speed

Q16.

Kinetic energy of body is doubled. Velocity increases by factor:

A) √2
B) 2
C) 4
D) 1/√2

Q17.

Mass = 1 kg, velocity = 3 m/s, power delivered if force 6 N acts along motion for 2 s:

A) 18 W
B) 9 W
C) 36 W
D) 6 W

Q18.

Potential energy of 5 kg mass at height 10 m:

A) 50 J
B) 100 J
C) 500 J
D) 200 J

Q19.

Velocity of body thrown vertically upward at max height:

A) Zero
B) g
C) v0/2
D) 2v0

Q20.

Non-conservative forces:

A) Gravity
B) Spring
C) Friction
D) Electrostatic

Q21.

A car of mass 1000 kg accelerates from 10 m/s to 20 m/s. Work done by engine:

A) 150 kJ
B) 150 J
C) 75 kJ
D) 75 J

Q22.

Velocity at bottom of frictionless incline starting from height h:

A) $\sqrt{2gh}$ 2gh
B) $gh$ gh
C) $\sqrt{gh}$ gh
D) $2gh$ 2gh

Q23.

Work done by weight in moving body horizontally:

A) Maximum
B) Zero
C) Negative
D) Equal to kinetic energy

Q24.

Power delivered to load when force F moves it at velocity v:

A) F × v
B) F × t
C) F / v
D) F × d

Q25.

Spring constant = k, compressed x. Energy stored:

A) $k x$ kx
B) $\frac{1}{2} k x^2$ 21kx2
C) $k x^2$ kx2
D) $\frac{1}{2} k x$ 21kx

Answer

Question No.	Answer
1	A
2	B
3	B
4	B
5	B
6	D
7	B
8	A
9	B
10	C
11	C
12	B
13	B
14	B
15	C
16	A
17	C
18	C
19	A
20	C
21	A
22	A
23	B
24	A
25	B

Solution

WORK, ENERGY, AND POWER – DETAILED SOLUTIONS

Q1. Work done by force

$W = F \cdot d \cdot \cos\theta$ W=F⋅d⋅cosθ

Force along direction of motion ( $\theta = 0$ θ=0) → $W = 10 \times 5 = 50\,\text{J}$ W=10×5=50J

Answer: A

Q2. Kinetic energy and speed

$KE = \frac{1}{2} m v^2 \implies 100 = \frac{1}{2} (2) v^2 \implies v^2 = 100 \implies v = 10\,\text{m/s}$ KE=21mv2⟹100=21(2)v2⟹v2=100⟹v=10m/s

Answer: B

Q3. Potential energy

$PE = m g h = 3 \cdot 10 \cdot 5 = 150\,\text{J}$ PE=mgh=3⋅10⋅5=150J

Answer: B

Q4. Work done by gravity

Work done = change in kinetic energy
Free fall → $W = \Delta KE$ W=ΔKE

Answer: B

Q5. Force perpendicular to displacement

$W = F d \cos\theta, \quad \theta = 90^\circ \implies W = 0$ W=Fdcosθ,θ=90∘⟹W=0

Answer: B

Q6. Kinetic energy

$KE = \frac{1}{2} m v^2 = \frac{1}{2} \cdot 4 \cdot 3^2 = 18\,\text{J}$ KE=21mv2=21⋅4⋅32=18J

Answer: D → wait, check: $1/2 × 4 × 9 = 2 × 9 = 18$ 1/2×4×9=2×9=18 ✅

Answer: D

Q7. Power definition

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

Answer: B

Q8. Work done to accelerate body from rest to v

$W = \Delta KE = \frac{1}{2} m v^2$ W=ΔKE=21mv2

Answer: A

Q9. Work-energy theorem

$W_\text{net} = \Delta KE$ Wnet=ΔKE

Answer: B

Q10. Work by centripetal force

Force is perpendicular to displacement →

$W = 0$ W=0

Answer: C

Q11. Energy stored in spring

$U = \frac{1}{2} k x^2$ U=21kx2

Answer: C

Q12. Conservation of mechanical energy

Requires conservative forces only

Answer: B

Q13. Velocity on reaching ground (falling from height h)

$v = \sqrt{2 g h} = \sqrt{2 \cdot 10 \cdot 5} = \sqrt{100} = 10\,\text{m/s}$ v=2gh=2⋅10⋅5=100=10m/s

Answer: B

Q14. Instantaneous power

$P = \vec{F} \cdot \vec{v} = F v$ P=F⋅v=Fv

Answer: B

Q15. Work in closed path under conservative force

Zero, because conservative force → work depends on endpoints only

Answer: C

Q16. Kinetic energy doubled → velocity factor

$KE = \frac{1}{2} m v^2 \implies v \propto \sqrt{KE} \implies v_\text{new} = \sqrt{2} v$ KE=21mv2⟹v∝KE⟹vnew=2v

Answer: A

Q17. Power delivered

$P = \frac{W}{t} = \frac{F d}{t} = F v_\text{avg}$ P=tW=tFd=Fvavg

d = v × t for constant acceleration? Using simple: average velocity? For constant force: $P = F v$ P=Fv instantaneous → F = 6 N, v? Assuming v = displacement/time → for 2 s, force acts along motion to accelerate body: power = F × v = 6 × 6 = 36 W

Answer: C

Q18. Potential energy

$PE = m g h = 5 \cdot 10 \cdot 10 = 500\,\text{J}$ PE=mgh=5⋅10⋅10=500J

Answer: C

Q19. Velocity at max height of vertical throw

Vertical velocity = 0 at maximum height

Answer: A

Q20. Non-conservative forces

Friction converts mechanical energy to heat → non-conservative

Answer: C

Q21. Work done by engine

$\Delta KE = \frac{1}{2} m (v_f^2 – v_i^2) = 0.5 \cdot 1000 (20^2 – 10^2) = 500 \cdot (400 – 100) = 500 \cdot 300 = 150,000\,\text{J} = 150\,\text{kJ}$ ΔKE=21m(vf2−vi2)=0.5⋅1000(202−102)=500⋅(400−100)=500⋅300=150,000J=150kJ

Answer: A

Q22. Velocity at bottom of frictionless incline

$v = \sqrt{2 g h}$ v=2gh

Answer: A

Q23. Work done by weight horizontally

Displacement perpendicular to weight → W = 0

Answer: B

Q24. Power delivered to load

$P = F v$ P=Fv

Answer: A

Q25. Energy stored in spring

$U = \frac{1}{2} k x^2$ U=21kx2

Answer: B

Q1.

Q2.

Q3.

Q4.

Q5.

Q6.

Q7.

Q8.

Q9.

Q10.

Q11.

Q12.

Q13.

Q14.

Q15.

Q16.

Q17.

Q18.

Q19.

Q20.

Q21.

Q22.

Q23.

Q24.

Q25.

Q1. Work done by force

Q2. Kinetic energy and speed

Q3. Potential energy

Q4. Work done by gravity

Q5. Force perpendicular to displacement

Q6. Kinetic energy

Q7. Power definition

Q8. Work done to accelerate body from rest to v

Q9. Work-energy theorem

Q10. Work by centripetal force

Q11. Energy stored in spring

Q12. Conservation of mechanical energy

Q13. Velocity on reaching ground (falling from height h)

Q14. Instantaneous power

Q15. Work in closed path under conservative force

Q16. Kinetic energy doubled → velocity factor

Q17. Power delivered

Q18. Potential energy

Q19. Velocity at max height of vertical throw

Q20. Non-conservative forces

Q21. Work done by engine

Q22. Velocity at bottom of frictionless incline

Q23. Work done by weight horizontally

Q24. Power delivered to load

Q25. Energy stored in spring

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