Problem 7PE

A shopper pushes a grocery cart 20.0 m at constant speed on level ground, against a 35.0 N frictional force. He pushes in a direction 25.0º below the horizontal. (a) What is the work done on the cart by friction? (b) What is the work done on the cart by the gravitational force? (c) What is the work done on the cart by the shopper? (d) Find the force the shopper exerts, using energy considerations. (e) What is the total work done on the cart?

Solution

Step 1 of 5

The man pushes the cart in a direction below the horizontal at a constant speed against a friction force.

a) We need to find out the work done on the cart by friction.

The work done by the friction is in the opposite direction of motion.

So the work done by friction is given by

The angle

So

F is the frictional force

d is the distance,