,A car has a mass of 1200 kg and is travelling at 15 m/s.
What is its kinetic energy?
A. 90,000 J
B. 135,000 J
C. 180,000 J
D. 270,000 J
Correct Answer: B
Rationale:
KE = 1/2 × m × v²
KE = 1/2 × 1200 × 15²
KE = 600 × 225
KE = 135,000 J
Question 2
A 4.0 kg object is lifted vertically through 8.0 m. The gravitational field strength is 9.8 N/kg.
What is the increase in gravitational potential energy?
A. 31.4 J
B. 39.2 J
C. 313.6 J
D. 784 J
Correct Answer: C
Rationale:
PE = m × g × h
PE = 4.0 × 9.8 × 8.0
PE = 313.6 J
Question 3
A ball falls from a height without air resistance.
Which statement correctly describes the energy transfer?
A. Kinetic energy decreases while gravitational potential energy increases.
B. Gravitational potential energy decreases while kinetic energy increases.
,C. Both gravitational potential energy and kinetic energy decrease.
D. Both gravitational potential energy and kinetic energy increase.
Correct Answer: B
Rationale:
As the ball falls, its height decreases, so its gravitational potential energy decreases. Its speed
increases, so its kinetic energy increases.
For an ideal situation:
E_total = PE + KE
The total mechanical energy remains constant.
Question 4
Two cars have the same mass. Car A travels at 20 m/s and Car B travels at 40 m/s.
How does the kinetic energy of Car B compare with Car A?
A. Twice as large
B. Three times as large
C. Four times as large
D. Eight times as large
Correct Answer: C
Rationale:
Kinetic energy is proportional to velocity squared.
Doubling the velocity gives:
2² = 4
Therefore, Car B has four times the kinetic energy.
Question 5
A machine receives 800 J of energy and transfers 600 J usefully.
What is the efficiency?
A. 25%
B. 60%
, C. 75%
D. 133%
Correct Answer: C
Rationale:
Efficiency = useful energy output ÷ total energy input × 100
Efficiency = 600 ÷ 800 × 100
= 75%
Question 6
A 2.5 kW heater is operated for 24 minutes.
How much energy is transferred in kWh?
A. 0.6 kWh
B. 1.0 kWh
C. 1.2 kWh
D. 60 kWh
Correct Answer: C
Rationale:
24 minutes = 24 ÷ 60 = 0.4 hours.
Energy = power × time
Energy = 2.5 × 0.4
= 1.0 kWh
Correct Answer: B
Question 7
A 1500 W appliance operates for 40 seconds.
How much energy does it transfer?
A. 37.5 J
B. 600 J
C. 60,000 J
D. 375,000 J
What is its kinetic energy?
A. 90,000 J
B. 135,000 J
C. 180,000 J
D. 270,000 J
Correct Answer: B
Rationale:
KE = 1/2 × m × v²
KE = 1/2 × 1200 × 15²
KE = 600 × 225
KE = 135,000 J
Question 2
A 4.0 kg object is lifted vertically through 8.0 m. The gravitational field strength is 9.8 N/kg.
What is the increase in gravitational potential energy?
A. 31.4 J
B. 39.2 J
C. 313.6 J
D. 784 J
Correct Answer: C
Rationale:
PE = m × g × h
PE = 4.0 × 9.8 × 8.0
PE = 313.6 J
Question 3
A ball falls from a height without air resistance.
Which statement correctly describes the energy transfer?
A. Kinetic energy decreases while gravitational potential energy increases.
B. Gravitational potential energy decreases while kinetic energy increases.
,C. Both gravitational potential energy and kinetic energy decrease.
D. Both gravitational potential energy and kinetic energy increase.
Correct Answer: B
Rationale:
As the ball falls, its height decreases, so its gravitational potential energy decreases. Its speed
increases, so its kinetic energy increases.
For an ideal situation:
E_total = PE + KE
The total mechanical energy remains constant.
Question 4
Two cars have the same mass. Car A travels at 20 m/s and Car B travels at 40 m/s.
How does the kinetic energy of Car B compare with Car A?
A. Twice as large
B. Three times as large
C. Four times as large
D. Eight times as large
Correct Answer: C
Rationale:
Kinetic energy is proportional to velocity squared.
Doubling the velocity gives:
2² = 4
Therefore, Car B has four times the kinetic energy.
Question 5
A machine receives 800 J of energy and transfers 600 J usefully.
What is the efficiency?
A. 25%
B. 60%
, C. 75%
D. 133%
Correct Answer: C
Rationale:
Efficiency = useful energy output ÷ total energy input × 100
Efficiency = 600 ÷ 800 × 100
= 75%
Question 6
A 2.5 kW heater is operated for 24 minutes.
How much energy is transferred in kWh?
A. 0.6 kWh
B. 1.0 kWh
C. 1.2 kWh
D. 60 kWh
Correct Answer: C
Rationale:
24 minutes = 24 ÷ 60 = 0.4 hours.
Energy = power × time
Energy = 2.5 × 0.4
= 1.0 kWh
Correct Answer: B
Question 7
A 1500 W appliance operates for 40 seconds.
How much energy does it transfer?
A. 37.5 J
B. 600 J
C. 60,000 J
D. 375,000 J
