Question 1:

The correct formula for efficiency is:

This matches option A.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 2:

We have:

• Total G.P.E. input = 2000 J

• Useful KE output = 1400 J

Efficiency formula:

Efficiency=(useful energy output) / (total energy input) ×100%

Efficiency=1400/2000×100=0.7×100=70%

Answer: B. 70%

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 3:

The wasted energy in the Sankey diagram is the energy that is not converted into useful kinetic energy (1400 J).

Since the total input is 2000 J, the wasted energy is:

In a skateboarder rolling downhill, the main cause of energy loss (wasted energy) is friction between the wheels and the ground, and air resistance, which both convert mechanical energy into thermal energy (heat).

Therefore, the missing label 'X' is likely to be:

D. Thermal energy from friction.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 4:

We already calculated:

• Energy in X = wasted energy = 2000−1400=600 J

• Percentage for X = 600/2000×100%=30%

So the correct pair is:

Energy in X (J) = 600
Energy in X (%) = 30

That matches option A.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 5:

The symbol 'W' in '40 W' stands for Watts, which is the unit of power (rate of energy transfer per second).

• Work Done is measured in joules (J), not watts.

• Weight is a force measured in newtons (N).

• Wasted energy is measured in joules (J).

• Watts (W) is the correct unit for power.

Answer: D. Watts

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 6:

From the Sankey diagram:

• Useful electrical power output = 40 W

• Wasted heat power = 120 W

Total power input = Useful output + Wasted output

Answer: D. 160 W

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 7:

Efficiency formula:

Given:

• Useful output = 40 W

• Total input = 160 W

Answer: D. 25%

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 8:

The statement describes that energy cannot be created or destroyed, only transferred, stored, or dissipated. This is known as the law of conservation of energy.

Answer: D. conservation of energy

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 9:

Recall that:

So:

Answer: C. 200 W

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 10:

We know:

• Useful power output = 0.2 kW

• Efficiency = 20%=0.20

Using the efficiency formula:

Efficiency=(useful energy output) / (total energy input)

0.20= 0.2 kW /(input)

Input=0.2/0.20=1 (kW)

Answer: A. 1 kW

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.