A 10 kg box, initially at rest, moves along a frictionless horizontal surface. A

Question

A 10 kg box, initially at rest, moves along a frictionless horizontal surface. A horizontal force to the right is applied to the box. The magnitude of the force changes as a function of time as shown.

1. Rank the impulse applied to the box by this force during each 2-second interval indicated below.

A. 0 to 2 s B. 2 to 4 s C. 4 to 6 s D. 6 to 8 s E. 8 to 10 s '

Explain your reasoning?

2. Assume no other horizontal forces act on the box. If the box was initially moving at 5.0 m/s to the left at t = 0 s, what is its speed at: (show your work!)

a. t = 2.0 s

b. t = 4.0 s

c. t = 6.0 s

d. t = 8.0 s

e. t = 10.0 s

Explanation / Answer

1. The area under the curve is the impulse

The area under the curve is0-2 secs 1/2 *2 *2 = 2 N.s

2-4 secs 2 *2 = 4 N.s

4-6 secs 2 + 1 = 3N.s

6-8 secs 1.25 N.s

8-10 secs is 0 N.s

This is the largest area in the curve and hence the largest impulse

Answer is 2 to 4 seconds

2.

change in momentum = impulse

m(v - u) = impulse till that point

a) 10(v - 5) = 2

v = 5.2 m/sec

b) 10(v - 5) = 2+4

v = 5.6 m/sec

c) 10(v - 5) = 2+4+3

v = 5.9 m/sec

d) 10(v - 5) = 2+4+3+1.25

v = 6.025 m/sec

e) 10(v - 5) = 2+4+3+1.25

v = 6.025 m/sec

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