Question

Suppose that the air resistance a car encounters is independent of its speed. When the car travels at 15 m/s, its engine delivers 20 hp to its wheels. (a) What is the power delivered to the wheels when the car travels at 30 m/s?

a) 20 hp
b) 40 hp
c) 80 hp
d) 160 hp

Answer 1

When a car's speed doubles from 15 m/s to 30 m/s, and air resistance is constant, the power delivered to the wheels also doubles from 20 hp to 40 hp.

Step-by-step explanation:

The student's question deals with power delivered to a car's wheels at different speeds assuming air resistance is independent of speed. When a car's speed doubles, the power required to overcome air resistance under these conditions would also double because power is proportional to the velocity in this scenario.

If the car's engine delivers 20 hp at 15 m/s, then it would need to deliver double that power to maintain double the speed if air resistance is constant, which is not the usual case in the real world. Hence, the power delivered to the wheels when the car travels at 30 m/s would be 40 hp (Option b).