A shopper in a supermarket pushes a cart with a force of 31.0 N directed at an a

Question

A shopper in a supermarket pushes a cart with a force of 31.0 N directed at an angle of 25.0° 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 45.6-m-long aisle.
J

(bg) The shopper goes down the next aisle, pushing horizontally and maintaining the same speed as before. If the work done by frictional forces doesn't change, would the shopper's applied force be larger, smaller, or the same?

a)larger

b)smaller   

c)the same

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

a)The work is larger in part (a).

b)The work is larger in part (b).    

c)The work is the same in both parts.

Explanation / Answer

a)

work done by the shopper = Force * distance * cos(25)

work done by the shopper = 31 * 45.6 * cos(25)

work done by the shopper = 1281.2 J

the work done by the shopper is 1281.2 J

b)

here , the force is now horizontal

the applied force will be smaller

c)

as the frictonal force will be lower , as the noraml force will decrease ,

hence , the applied force is lower

hence , work done = force * distance

hence , a)The work is larger in part (a).

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