Previous IIT / JEE Objective Questions
Work, Energy & Power
This section contains previously asked and IIT-pattern objective questions from Work, Energy & Power. Each question includes:
- Correct answer
- Solution method
- Why IIT expects this approach
Q1. (IIT-JEE)
A particle moves on a rough horizontal surface with initial speed v. Coefficient of friction is μ. What distance will it travel before stopping?
Answer: v² / (2μg)
Solution Method:
Use Work–Energy Theorem.
Initial KE = Work done by friction ½mv² = μmg·s
s = v² / (2μg)
Examiner Note: Mass cancels — mass is a distraction.
Q2. (IIT-JEE)
A block slides down a smooth incline of height h. What is its speed at the bottom?
Answer: √(2gh)
Method:
Energy conservation:
mgh = ½mv²
Key Insight: Angle of incline is irrelevant.
Q3. (JEE Main)
A body is thrown vertically upward. At the highest point, which quantity is zero?
Answer: Velocity
Explanation:
- Velocity = 0
- Acceleration = g (non-zero)
- Force = mg (non-zero)
Q4. (IIT-JEE)
A particle moves in a circular path with constant speed. What is the work done by centripetal force?
Answer: 0
Method:
Centripetal force ⟂ velocity ⇒ F·v = 0
IIT Trap: Motion exists, but no energy change.
Q5. (IIT-JEE)
A particle has KE = 16 J. Its momentum is doubled. New kinetic energy is:
Answer: 64 J
Logic:
KE ∝ p² ⇒ KE becomes 4 times
Q6. (JEE Main)
A spring of constant k is compressed by x. Potential energy stored is:
Answer: ½kx²
Method:
Work done against variable force:
U = ∫kx dx = ½kx²
Q7. (IIT-JEE)
A particle loses half of its kinetic energy. Final speed is:
Answer: v / √2
Reason:
KE ∝ v²
Q8. (IIT-JEE)
A block moves with constant speed on a rough surface. Net work done on the block is:
Answer: 0
Explanation:
Constant speed ⇒ ΔKE = 0 ⇒ Net work = 0
Q9. (JEE Main)
Which force can never change kinetic energy?
Answer: Centripetal force
Why:
Always perpendicular to velocity.
Q10. (IIT-JEE)
A particle is projected vertically upward. Total mechanical energy during motion:
Answer: Constant
Condition:
Only gravity acts (conservative force).
Q11. (JEE Main)
Power delivered by a force is zero when:
Answer: Force ⟂ velocity
Formula:
P = F·v
Q12. (IIT-JEE)
A body slides down a rough incline. Which quantity decreases?
Answer: Mechanical energy
Reason:
Friction is non-conservative.
Q13. (JEE Main)
If speed is doubled, kinetic energy becomes:
Answer: Four times
Q14. (IIT-JEE)
A particle moves under a conservative force. Work done depends on:
Answer: Initial and final positions only
Q15. (JEE Main)
At turning point of motion, which quantity is zero?
Answer: Kinetic energy
Final Exam Tip
Most objective questions in Work–Energy are decided by logic, not calculation.
Work, Energy & Power – Complete Physics Library
This is the MASTER LIBRARY PAGE for the complete chapter Work, Energy and Power, prepared for Intermediate, IIT-JEE (Main & Advanced), NEET and competitive exams.
All concepts are explained from basic to IIT level, including theory, derivations, numerical problems, objective questions, previous year questions, tough IIT problems, tricks and cautions.
📚 Complete Lesson Index (Part 1 – Part 39)
- Part 1 – Introduction to Work
- Part 2 – Types of Work
- Part 3 – Variable Force & Graphs
- Part 4 – Kinetic Energy
- Part 5 – Work–Energy Theorem
- Part 6 – Potential Energy
- Part 7 – Conservative Forces
- Part 8 – Mechanical Energy
- Part 9 – Power
- Part 10 – Power Applications
- Part 11
- Part 12
- Part 13
- Part 14
- Part 15
- Part 16
- Part 17
- Part 18
- Part 19
- Part 20
- Part 21
- Part 22
- Part 23
- Part 24
- Part 25
- Part 26
- Part 27
- Part 28
- Part 29
- Part 30
- Part 31
- Part 32
- Part 33
- Part 34
- Part 35
- Part 36
- Part 37
- Part 38
- Part 39 – Final IIT Tough Problems & Solutions
Prepared by: Shaktimatha Learning 🌱
Strong Concepts • Smart Practice • Exam Success
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