College Physics with MasteringPhysics 7th Edition by Jerry Wilson,Anthony Buffa,Bo Lou

تمرين 16

A sleigh and driver with a total mass of 120 kg are pulled up a hill with a 15° incline by a horse, as illustrated in Fig. (a) If the overall retarding frictional force is 950 N and the sled moves up the hill with a constant velocity of 5.0 km/h, what is the power output of the horse (Express in horsepower, of course. Note the magnitude of your answer, and explain.) (b) Suppose that in a spurt of energy, the horse accelerates the sled uniformly from 5.0 km/h to 20 km/h in 5.0 s. What is the horse's maximum instantaneous power output Assume the same force of friction.

FIGURE A one-horse open sleigh See Exercise.