Question

A shopper pushes a grocery cart for a distance 19 M at a constant speed on level ground, against a 25 N frictional force. He pushes in a direction 25.5 degrees below the horizontal.

Answer 1

(a) What is the work done on the cart by friction?

$W_f=-25\cdot19=-475\ (J)$

(b) What is the work done on the cart by the gravitational force?

$W_g=0\ (J)$

(c) What is the work done on the cart by the shopper?

$W_s=-W_f=475\ (J)$

(d) Find the forces the shopper exerts, using energy considerations.

$F\cdot\cos25.5°-25=0\to F=27.7\ (N)$

(e) what is the total work done on the cart?

$W_t=475-475+0=0\ (J)$