AP Physics 1 Question 389: Answer and Explanation

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Question: 389

7. A car with a mass of 1000 kg experiences a frictional force of 3500 N while driving at a constant speed of a 15 m/s. What is the power output of the car's engine?

  • A. 3.5 kW
  • B. 5.25 kW
  • C. 35.0 kW
  • D. 52.5 kW

Correct Answer: D



In order to maintain a constant speed, the net force on the car must be zero. This means that the car's engine must be applying a force equal in magnitude but opposite in direction to the frictional force. The equation P = Fv then yields

P = Fv = 3500 N ยท 15 m/s = 52,500 W = 52.5 kW