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# A shopper in a supermarket pushes a cart with a force of 34 N directed at an angle of 25° below the horizontal. ?

A shopper in a supermarket pushes a cart with a force of 34 N directed at an angle of 25° below the horizontal. The force is just sufficient to overcome various frictional forces, so the cart moves at constant speed.

(a) Find the work done by the shopper as she moves down a 64.0-m length aisle.

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(b) What is the net work done on the cart?

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Why?

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

### 1 Answer

- oubaasLv 72 months ago
(a) Find the work W done by the shopper as she moves down a 64.0-m length aisle.

W = F*cos 25*d = 34*0.906*64 = 1970 joule(2.0*10^3 with just 2 sign. digits)

(b) What is the net work W' done on the cart?

W' = 0, since it moves at constant speed and applied force is counteracted by friction

(c) 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 F' be larger, smaller, or the same?

F' = F*cos 25° , then F' < F since cos 25° < 1

What about the work W'' done on the cart by the shopper?

W'' = W , since F' = F*cos 25°