A worker is pushing a cart along the floor. At first, the worker has to push har

Question

A worker is pushing a cart along the floor. At first, the worker has to push hard in order to get the cart moving. After a while, it is easier to push and he keeps it going at a uniform speed. Finally, the worker has to pull back on the cart in order to bring it to a stop before it hits the wall. The force exerted by the worker on the cart is purely horizontal. Take the direction the worker is going as positive.

Below are shown graphs of some of the physical variables of the problem. Match the graphs with the variables in the list at the left below. You may use a graph more than once or not at all. (Note: the time axes are to the same scale, but the ordinate ("y-axes") are not, and t = 0 is just as the cart starts moving.)

(a)

friction force on the cart  ---Select--- A B C D E N  
Explain your choice.

(b)

force exerted by the worker on the cart  ---Select--- A B C D E N  
Explain your choice.

(c)

net force experienced by the cart  ---Select--- A B C D E N  
Explain your choice.

(d)

acceleration of the cart  ---Select--- A B C D E N  
Explain your choice.

(e)

velocity of the cart  ---Select--- A B C D E N  
Explain your choice.

Explanation / Answer

(a)

Friction force-

Friction force is constant during motion.

so, graph (A) is choice of answer.

(b)

Force by worker-

First force is constant then it decreases and finaly goes negative.

so, answer for force exerted by worker is graph (E)

(c)

Net force on cart-

As given that the cart initial accelerate, then do uniform motion and then deccelerate.

so, answer should be graph (C)

(d)

Acceleration of cart-

As given that the cart initial accelerate, then do uniform motion and then deccelerate.

so, answer is graph (C)

(e)

velocity of cart-

As given that initialy speed is increasing then  it going at a uniform speed.   Finally, the worker has to pull back on

the cart in order to bring it to a stop.

so, graph for velocity is (B).

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