9702_s22_qp_13 Question 18

A car of weight 15 000 N is travelling along a horizontal road. 

At one instant, the thrust force acting on the car from the engine is 12 000 N and the resistive force acting on the car is 3 000 N. The velocity of the car at this instant is 24 m s^–1. 

What is the power output from the engine? 

A 72 kW 

B 220 kW 

C 290 kW 

D 360 kW

ANSWER: C

The Physics Behind answer:

• Power at an instant is the product of force and speed at that instant.
• Since the power being asked is the output from the engine, then the answer is the product of 12 000 N and 24 m s^–1.
• The product is rounded off to 2 significant figures following the number of significant figures of the speed.