Question

You are testing a new car in a wind-tunnel for road and wind resistance. At speed of 90.0 km/h you have found that 74.0 % of the total output power of an automobile engine is used in overcoming the resistance of the road and wind against the movement of the car. If the output of a particular car engine is 57.00 HP, what is this resistance (ie what is the force)? Give your answer in Newtons. (Take one HP as 745 Watts.)

Answer 1

Calculate the power requirement , 57 * 745 Watts.
That equals the resistance force times the velocity, if the velocity is in m/s.
Solve for the force. It will be in Newtons.