Question

A shopper in a supermarket pushes a cart with a force of 35.0 N directed at an angle of 25.08 below the horizontal. The force is just sufficient to balance various friction forces, so the cart moves at constant speed. (a) Find the work done by the shopper on the cart as she moves down a 50.0-m-long aisle. (b) The shopper goes down the next aisle, pushing horizontally and maintaining the same speed as before. If the friction force doesn’t change, would the shopper’s applied force be larger, smaller, or the same? (c) What about the work done on the cart by the shopper?

Answer 1

Answer:

a)1585 J

b)The applied force would be smaller and the work would again be zero

c)0 N

Explanation:

a)  The horizontal component of the applied force is 35 N x cos 25.08 = 31.70 N

Work = force x distance = 31.7 N x 50 m = 1,585 J

b)  If the applied force were horizontal, all of it would counter friction, so only 31.7 N would be needed.  The work done on the cart is zero because there is no change in mechanical energy.

c) The work done on the  cart by the shopper will be zero because there is no change in mechanical energy.