Class 9 • Physics • Chapter 9
Work and Energy
True & False Quiz
Work. KE. PE.
✓True
✗False
25
Questions
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Ch.9
Chapter
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IX
Class
Why True & False for Work and Energy?
How this format sharpens your conceptual clarity
🔵 Work and Energy introduces the most universal concept in all of science — energy conservation governs every process in the universe.
✅ T/F tests the scientific definition of work (W = F·d·cosθ), kinetic and potential energy formulae, power, and the law of conservation of energy.
🎯 Work done is ZERO if force and displacement are perpendicular (θ = 90°, cos90° = 0) — e.g. a porter walking horizontally while carrying a load on the head does NO work on the load.
📋
Read each statement carefully. Click True or False — instant feedback with explanation appears. Submit anytime; unattempted questions are marked Skipped.
Q 1
Work is said to be done only when a force is applied on an object and the object is displaced.
Q 2
If there is no displacement, work done is zero even if a large force is applied.
Q 3
Work can be positive, negative, or zero.
Q 4
When a coolie carries a load on his head and walks horizontally, he does positive work on the load.
Q 5
Work done against gravity in lifting an object is stored as potential energy in the object.
Q 6
Kinetic energy depends on both mass and velocity of the object.
Q 7
Potential energy of an object does not depend on the height of the object.
Q 8
The SI unit of work is joule (J).
Q 9
A body moving with uniform velocity does no work against friction.
Q 10
Power is the rate of doing work.
Q 11
The SI unit of power is watt.
Q 12
Energy and work have the same unit.
Q 13
When work is done on an object, its energy decreases.
Q 14
The sum of kinetic and potential energies of a body is called its total mechanical energy.
Q 15
In the absence of friction, the total mechanical energy of a system remains constant.
Q 16
The work done by gravity on a freely falling body is positive.
Q 17
The work done by friction is always positive.
Q 18
The commercial unit of energy is kilowatt-hour (kWh).
Q 19
If a body is moving horizontally, its potential energy changes continuously.
Q 20
Energy can neither be created nor destroyed; it can only change from one form to another.
Q 21
When a ball hits the ground and bounces back, energy is completely lost.
Q 22
Work done on an object is independent of the direction of force.
Q 23
When an object is thrown upwards, its kinetic energy increases with height.
Q 24
The power of a machine tells us how fast it can do work.
Q 25
A boy climbs a staircase slowly and another runs up quickly; both do the same work but have different power.
Key Takeaways — Work and Energy
Core facts for CBSE Boards & exams
1
Work (W) = Force × displacement × cosθ; unit = Joule (J); work is zero if F ⊥ displacement.
2
Kinetic Energy: KE = ½mv²; depends on mass and square of velocity.
3
Gravitational Potential Energy: PE = mgh; depends on mass, gravity, and height.
4
Law of Conservation of Energy: energy can neither be created nor destroyed, only transformed.
5
Power (P) = Work/Time = W/t; unit = Watt (W); 1 horse power = 746 W.
6
1 kWh = 3.6 × 10⁶ J = commercial unit of energy used for billing electricity.