Lesson 5 – Work, Energy and Power Short Questions & Answers – Set 2
Q1. State the conditions for work to be done.
Work is said to be done when a force acts on a body, the body undergoes displacement, and the displacement has a component along the direction of force.
Q2. Explain why pushing a wall does not involve work.
Though force is applied on the wall, there is no displacement. Hence, work done is zero.
Q3. What is the work done when force is perpendicular to displacement?
When force is perpendicular to displacement, the work done is zero.
Q4. Define mechanical energy.
Mechanical energy is the sum of kinetic energy and potential energy of a body.
Q5. Write the relation between work and energy.
Work done on a body is equal to the change in its energy.
Q6. What happens to the kinetic energy of a body if its speed becomes zero?
When speed becomes zero, the kinetic energy of the body becomes zero.
Q7. Why is kinetic energy always positive?
Kinetic energy depends on the square of velocity, which is always positive.
Q8. What is average power?
Average power is defined as the total work done divided by the total time taken.
Q9. What is the relation between power, force, and velocity?
Instantaneous power is given by the relation P = F · v.
Q10. State the work–energy theorem.
The work done by the net force acting on a body is equal to the change in its kinetic energy.
Q11. Why does a fast-moving body possess more kinetic energy?
Kinetic energy depends on the square of velocity. Hence, higher velocity results in greater kinetic energy.
Q12. Distinguish between average power and instantaneous power.
Average power is calculated over a time interval, whereas instantaneous power is calculated at a particular instant.
Q13. What is the work done by gravity on a freely falling body?
The work done by gravity on a freely falling body is positive.
Q14. Why is friction called a non-conservative force?
Friction depends on the path followed and converts mechanical energy into heat energy.
Q15. Write one practical application of work–energy theorem.
The work–energy theorem is used to calculate the speed of a body without finding time or acceleration.
Exam Tip (2–3 Marks)
- Write answers in short paragraphs.
- Use proper scientific terms.
- Underline keywords if possible.
“Short answers need clarity, not length.”
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 🌱
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