Question

What is the minimum power required for heat engine to lift a 80 kg mass 5 m in 20 s if it releases 1000 J of heat energy from its exhaust each second?

• A. 200 w
• B. 500 w
• C. 1200 w
• D. 3000 w

Hint:

When calculating power, always consider both the work done and the heat released.

Answer 1

The Correct Option is C

To calculate the minimum power, we need to consider the work done in lifting the object. The work done in lifting is: \[ W = mgh = 80 \times 9.8 \times 5 = 3920 \, {J} \] Now, the power is given by the formula: \[ P = \frac{W}{t} = \frac{3920}{20} = 196 \, {W} \] However, the heat released is 1000 J per second, so the total power required will be: \[ P_{total} = 196 \, {W} + 1000 \, {W} = 1200 \, {W} \] Thus, the correct answer is (c) 1200 W.