Q.1 Work done is said to be zero when:
Force is applied but no displacement occurs
Displacement occurs without any force
Force is perpendicular to displacement
Both A and C
Explanation - Work is the dot product of force and displacement. If there is no displacement, or force is perpendicular to displacement, work done is zero.
Correct answer is: Both A and C
Q.2 What is the SI unit of work?
Newton
Joule
Watt
Pascal
Explanation - Work is defined as force multiplied by displacement. Its SI unit is Joule (N·m).
Correct answer is: Joule
Q.3 A force of 10 N displaces a body by 5 m in the direction of force. Work done is:
2 J
15 J
50 J
5 J
Explanation - Work done W = F × d = 10 × 5 = 50 J.
Correct answer is: 50 J
Q.4 Power is defined as:
Work per unit force
Work per unit time
Force per unit work
Energy × Time
Explanation - Power is the rate at which work is done, i.e., Work/Time.
Correct answer is: Work per unit time
Q.5 What is the SI unit of power?
Joule
Newton
Watt
Pascal
Explanation - Power is measured in Watt (1 W = 1 J/s).
Correct answer is: Watt
Q.6 Kinetic energy depends on:
Velocity only
Mass only
Mass and velocity
Acceleration
Explanation - Kinetic energy KE = ½mv², so it depends on both mass and velocity.
Correct answer is: Mass and velocity
Q.7 Potential energy is energy possessed due to:
Motion
Configuration or position
Temperature
Pressure
Explanation - Potential energy is stored energy due to position or configuration, e.g., mgh.
Correct answer is: Configuration or position
Q.8 Work done against gravity is stored as:
Kinetic energy
Potential energy
Heat
Power
Explanation - When work is done against gravity, it increases gravitational potential energy (mgh).
Correct answer is: Potential energy
Q.9 A body of mass 2 kg is raised to a height of 10 m. Potential energy gained is:
20 J
100 J
200 J
50 J
Explanation - PE = mgh = 2 × 9.8 × 10 ≈ 200 J.
Correct answer is: 200 J
Q.10 Which of the following is not a form of mechanical energy?
Kinetic energy
Potential energy
Heat energy
Elastic energy
Explanation - Heat energy is thermal, not mechanical. Mechanical energy includes kinetic and potential.
Correct answer is: Heat energy
Q.11 The work done by friction is:
Always positive
Always negative
Zero
Sometimes positive, sometimes negative
Explanation - Friction always opposes motion, so work done by friction is negative.
Correct answer is: Always negative
Q.12 1 horsepower equals:
746 J
746 W
1000 W
1000 J
Explanation - 1 horsepower = 746 watts (approximately).
Correct answer is: 746 W
Q.13 Mechanical energy is the sum of:
Kinetic + Heat
Potential + Heat
Kinetic + Potential
Heat + Chemical
Explanation - Mechanical energy = KE + PE of the system.
Correct answer is: Kinetic + Potential
Q.14 Which law states that energy cannot be created or destroyed?
Newton's First Law
Conservation of Energy
Hooke’s Law
Pascal’s Law
Explanation - Law of conservation of energy: Energy can neither be created nor destroyed, only transformed.
Correct answer is: Conservation of Energy
Q.15 A boy lifts a box of 20 kg to a height of 2 m in 10 seconds. Power developed is approximately:
40 W
20 W
60 W
30 W
Explanation - Work = mgh = 20×9.8×2 = 392 J, Power = 392/10 ≈ 40 W.
Correct answer is: 40 W
Q.16 Work done in circular motion with constant speed is:
Positive
Negative
Zero
Constant
Explanation - In uniform circular motion, force is perpendicular to displacement, hence work = 0.
Correct answer is: Zero
Q.17 When velocity of a body doubles, its kinetic energy becomes:
Double
Four times
Half
Same
Explanation - KE ∝ v², so doubling velocity increases KE by 4 times.
Correct answer is: Four times
Q.18 Which quantity has the same unit as work?
Energy
Force
Power
Pressure
Explanation - Work and energy both are measured in Joules.
Correct answer is: Energy
Q.19 Work-energy theorem states:
Work done = Force × Displacement
Work done = Change in kinetic energy
Work done = Change in potential energy
Work done = Energy × Time
Explanation - According to the work-energy theorem, total work done on a body equals change in kinetic energy.
Correct answer is: Work done = Change in kinetic energy
Q.20 Which of the following is a non-conservative force?
Gravitational force
Elastic force
Electrostatic force
Frictional force
Explanation - Friction depends on path and dissipates energy as heat, so it is non-conservative.
Correct answer is: Frictional force
Q.21 Efficiency of a machine is the ratio of:
Output work to input work
Input work to output work
Power to energy
Energy to force
Explanation - Efficiency = Useful output work / Total input work × 100%.
Correct answer is: Output work to input work
Q.22 Work done by centripetal force is:
Positive
Negative
Zero
Maximum
Explanation - Centripetal force acts perpendicular to velocity, hence does no work.
Correct answer is: Zero
Q.23 Which has more kinetic energy at same speed?
A heavy truck
A light car
Both same
Depends on height
Explanation - KE = ½mv². At same speed, larger mass → greater KE.
Correct answer is: A heavy truck
Q.24 Unit of energy used in electricity bills is:
Joule
Watt
Kilowatt-hour
Newton
Explanation - Energy consumed is measured in kilowatt-hour (kWh).
Correct answer is: Kilowatt-hour
Q.25 If a spring is compressed, energy stored is:
Kinetic energy
Potential energy
Heat energy
Nuclear energy
Explanation - Compressed or stretched springs store elastic potential energy.
Correct answer is: Potential energy