Seed 121

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course Phy 121

Masses of 5 kg and 6 kg are suspended from opposite sides of a light frictionless pulley and are released. •What will be the net force on the 2-mass system and what will be the magnitude and direction of its acceleration?

answer/question/discussion:

5kg *-9.8m/s/s

6kg * 9.8m.s.s

Fnet = -49N +58.8N = 9.8N

9.8N = 11kg * a

A = .89m/s/s

The acceleration will be in the direction of the heavier side (6kg).

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• If you give the system a push so that at the instant of release the 5 kg object is descending at 1.8 meters / second, what will be the speed and direction of motion of the 5 kg mass 1 second later?

answer/question/discussion:

5kg * 9.8m/s/s = 49N

6kg *9.8m/s/s = -58.8

V0 = 1.8m/s

T = 1s

Fnet = 49N - 58.8N = -9.8N

-9.8N / 11kg = a = -.89m/s/s

-.89m/s/s = vf - 1.8m/s / 1s

Vf = .91m/s

vAve = .91m/s - .89m/s / 2 = .01m/s = speed

This speed will be in the direction of the heavier wait, so in this case, positive.

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• During the first second, are the velocity and acceleration of the system in the same direction or in opposite directions, and does the system slow down or speed up?

answer/question/discussion:

The velocity and acceleration are in opposite directions. The system slows down, reaches zero, then speeds up again in the opposite direction.

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