Q.1 Work is said to be done when:
A force is applied but there is no displacement
A force causes displacement in the direction of the force
There is only displacement without any force
The force is perpendicular to displacement
Explanation - Work is done only when a force causes displacement and has a component in the direction of displacement.
Correct answer is: A force causes displacement in the direction of the force
Q.2 The SI unit of work is:
Newton
Joule
Watt
Pascal
Explanation - Work is measured in joules, where 1 joule = 1 newton × 1 meter.
Correct answer is: Joule
Q.3 A man pushes a wall but the wall does not move. The work done is:
Positive
Negative
Zero
Maximum
Explanation - No displacement occurs, so work done is zero despite the force applied.
Correct answer is: Zero
Q.4 Which of the following is a scalar quantity?
Force
Work
Momentum
Displacement
Explanation - Work has magnitude but no direction, making it a scalar quantity.
Correct answer is: Work
Q.5 When a body moves with constant velocity, the work done by net force is:
Positive
Negative
Zero
Cannot be determined
Explanation - At constant velocity, there is no net acceleration, hence net force and net work done are zero.
Correct answer is: Zero
Q.6 Which of the following is the correct unit of power?
Joule
Newton
Watt
Pascal
Explanation - Power is the rate of doing work and is measured in watts (W).
Correct answer is: Watt
Q.7 Power is defined as:
Work done divided by force
Force divided by time
Work done divided by time
Work done multiplied by time
Explanation - Power represents the rate at which work is done or energy is transferred per unit time.
Correct answer is: Work done divided by time
Q.8 A 20 kg object is lifted vertically upward through a distance of 5 m. The work done against gravity is (g = 10 m/s²):
50 J
1000 J
200 J
2000 J
Explanation - Work done = m × g × h = 20 × 10 × 5 = 1000 J.
Correct answer is: 1000 J
Q.9 If the kinetic energy of a body is doubled, its velocity will:
Remain the same
Double
Increase by √2 times
Increase by four times
Explanation - KE = ½ mv². Doubling KE implies v becomes √2 times the initial velocity.
Correct answer is: Increase by √2 times
Q.10 The work done in moving an object horizontally on a frictionless surface is:
Positive
Negative
Zero
Dependent on speed
Explanation - Any applied force causing displacement on a frictionless surface does positive work.
Correct answer is: Positive
Q.11 The work-energy theorem states:
Work done = Force × Time
Work done equals change in potential energy
Work done equals change in kinetic energy
Work done equals mass × acceleration
Explanation - The theorem directly relates net work done on an object to its change in kinetic energy.
Correct answer is: Work done equals change in kinetic energy
Q.12 Potential energy depends on:
Mass and speed
Mass and height
Velocity and height
Force and speed
Explanation - Potential energy due to gravity is given by PE = mgh, depending on mass and height.
Correct answer is: Mass and height
Q.13 The work done by gravity on a falling body is:
Always positive
Always negative
Zero
Sometimes positive, sometimes negative
Explanation - Gravity acts in the same direction as displacement, hence work is always positive.
Correct answer is: Always positive
Q.14 If force and displacement are at right angles, the work done is:
Maximum
Zero
Negative
Minimum but not zero
Explanation - Work done = F × d × cosθ. For θ = 90°, cosθ = 0, so work done is zero.
Correct answer is: Zero
Q.15 The area under a Force-Displacement graph represents:
Power
Velocity
Work done
Acceleration
Explanation - The integral of force with respect to displacement gives work done.
Correct answer is: Work done
Q.16 The kinetic energy of a body of mass m and velocity v is:
mv
mv²
½ mv²
2mv
Explanation - Kinetic energy is given by the formula KE = ½ mv².
Correct answer is: ½ mv²
Q.17 A device used to measure power of an engine is called:
Dynamometer
Barometer
Anemometer
Voltmeter
Explanation - Dynamometers are specifically used to measure engine power output.
Correct answer is: Dynamometer
Q.18 A body of mass 10 kg is moving with velocity 2 m/s. Its kinetic energy is:
10 J
20 J
5 J
40 J
Explanation - KE = ½ mv² = ½ × 10 × (2)² = 20 J.
Correct answer is: 20 J
Q.19 Which of the following statements about energy is true?
Energy can be created
Energy can be destroyed
Energy can only change form
Energy always decreases
Explanation - The law of conservation of energy states energy cannot be created or destroyed.
Correct answer is: Energy can only change form
Q.20 Horsepower is a unit of:
Force
Energy
Work
Power
Explanation - Horsepower is a non-SI unit used to measure power.
Correct answer is: Power
Q.21 If work done is zero, which of the following is true?
Force is zero
Displacement is zero
Force is perpendicular to displacement
All of the above
Explanation - Work done can be zero if there is no force, no displacement, or force is perpendicular to displacement.
Correct answer is: All of the above
Q.22 Which of these is not an example of potential energy?
Stretched spring
Water in a reservoir
Running athlete
Charged battery
Explanation - A running athlete possesses kinetic energy, not potential energy.
Correct answer is: Running athlete
Q.23 The power output when 1000 J of work is done in 2 seconds is:
500 W
2000 W
250 W
100 W
Explanation - Power = Work / Time = 1000 / 2 = 500 W.
Correct answer is: 500 W
Q.24 The work done by friction is always:
Positive
Negative
Zero
Sometimes positive, sometimes negative
Explanation - Friction opposes motion, so it always does negative work.
Correct answer is: Negative
Q.25 The law of conservation of energy states that:
Energy can be created but not destroyed
Energy can be destroyed but not created
Energy can neither be created nor destroyed, only transformed
Energy is always constant in a system
Explanation - According to the law of conservation of energy, total energy remains constant and can only change form.
Correct answer is: Energy can neither be created nor destroyed, only transformed
Q.26 A body moves 5 m under the influence of a force of 10 N in the opposite direction. Work done is:
50 J
-50 J
0 J
25 J
Explanation - Since force and displacement are opposite, work done is negative: W = -10 × 5 = -50 J.
Correct answer is: -50 J
Q.27 The kinetic energy of a body depends directly on:
Velocity only
Mass only
Square of velocity
Height only
Explanation - KE = 1/2 × m × v², so it depends on the square of the velocity.
Correct answer is: Square of velocity
Q.28 The total mechanical energy in a perfectly isolated system:
Increases
Decreases
Remains constant
Becomes zero
Explanation - In the absence of external forces, total mechanical energy remains constant.
Correct answer is: Remains constant
Q.29 The work done by a conservative force around a closed path is:
Positive
Negative
Zero
Constant
Explanation - For conservative forces, work done over a closed loop is zero.
Correct answer is: Zero
Q.30 A body of 2 kg mass is lifted vertically by 1.5 m. The potential energy gained is:
9.8 J
29.4 J
19.6 J
14.7 J
Explanation - PE = m × g × h = 2 × 9.8 × 1.5 = 29.4 J.
Correct answer is: 29.4 J
Q.31 The unit of work in the CGS system is:
Erg
Dyne
Calorie
Joule
Explanation - In the CGS system, work is measured in ergs, where 1 erg = 10^-7 Joules.
Correct answer is: Erg
Q.32 Which of the following is NOT an example of potential energy?
A stretched spring
Water stored at height
A moving car
A compressed gas
Explanation - A moving car has kinetic energy, not potential energy.
Correct answer is: A moving car
Q.33 Work-energy theorem is based on the relation between:
Force and velocity
Force and displacement
Kinetic energy and work
Mass and velocity
Explanation - The work-energy theorem directly relates work done to the change in kinetic energy of a body.
Correct answer is: Kinetic energy and work
Q.34 If an object falls freely from a height, the sum of potential and kinetic energy:
Increases
Decreases
Remains constant
Becomes zero
Explanation - In the absence of air resistance, total mechanical energy remains constant.
Correct answer is: Remains constant
Q.35 A body of mass 3 kg is moving with velocity 4 m/s. Its kinetic energy is:
6 J
12 J
24 J
48 J
Explanation - KE = 1/2 × m × v² = 0.5 × 3 × 16 = 24 J.
Correct answer is: 24 J
Q.36 A 50 W device runs for 2 hours. Energy consumed is:
0.05 kWh
0.1 kWh
0.2 kWh
1 kWh
Explanation - Energy = Power × Time = 50 × 2 = 100 Wh = 0.1 kWh.
Correct answer is: 0.1 kWh
Q.37 In a perfectly elastic collision, which of the following is conserved?
Kinetic energy only
Potential energy only
Both kinetic energy and momentum
Momentum only
Explanation - In elastic collisions, both momentum and kinetic energy are conserved.
Correct answer is: Both kinetic energy and momentum
Q.38 The energy possessed by a body due to motion is proportional to:
Velocity
Velocity squared
Acceleration
Height
Explanation - Kinetic energy is proportional to the square of velocity.
Correct answer is: Velocity squared
Q.39 If a spring constant is 100 N/m and it is compressed by 0.1 m, the potential energy stored is:
0.1 J
0.25 J
0.5 J
1 J
Explanation - PE = 1/2 × k × x² = 0.5 × 100 × (0.1)² = 0.5 J.
Correct answer is: 0.5 J
Q.40 When velocity doubles, kinetic energy:
Doubles
Quadruples
Remains constant
Halves
Explanation - KE is proportional to the square of velocity. Doubling velocity increases KE by four times.
Correct answer is: Quadruples
Q.41 In hydroelectric plants, the type of energy conversion is:
Electrical to mechanical
Potential to electrical
Kinetic to electrical
Heat to electrical
Explanation - Water stored at a height has potential energy, which is converted to electrical energy via turbines and generators.
Correct answer is: Potential to electrical
Q.42 A person pushes a car with force 400 N over a distance of 10 m. Work done is:
40 J
4000 J
4 J
100 J
Explanation - Work = Force × Distance = 400 × 10 = 4000 J.
Correct answer is: 4000 J
Q.43 Which of the following forces is non-conservative?
Gravity
Electrostatic force
Friction
Elastic spring force
Explanation - Friction is a non-conservative force as energy is lost as heat and cannot be fully recovered.
Correct answer is: Friction
Q.44 The gravitational potential energy of an object depends on:
Height only
Mass only
Both mass and height
Velocity
Explanation - PE = m × g × h, so it depends on both mass and height.
Correct answer is: Both mass and height
Q.45 The work done by a machine is equal to:
Force × Displacement
Power × Time
Energy transferred
All of the above
Explanation - Work done can be expressed in different ways, all are equivalent representations.
Correct answer is: All of the above
Q.46 The power output of a motor that does 12,000 J of work in 60 seconds is:
100 W
150 W
200 W
250 W
Explanation - Power = Work / Time = 12,000 / 60 = 200 W.
Correct answer is: 200 W
Q.47 A rolling ball eventually comes to rest because of:
Gravity
Elastic collision
Friction
Inertia
Explanation - Friction opposes motion and converts kinetic energy into heat, bringing the ball to rest.
Correct answer is: Friction
Q.48 In a perfectly efficient machine, the input work is equal to:
Zero
Output work
Twice the output work
Half the output work
Explanation - In an ideal machine, no energy is lost, so input work equals output work.
Correct answer is: Output work