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course PHY 121
3.27.11 at 4:41 pm
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/sec^2 = 49 Netwons
6kg * 9.8m/sec^2 = 58.8 Netwons
49 + 58.8 = 107.8 Newtons
a = Fnet/m
= 58.8/11kg = 5.35m/sec^2
Acceleration will change directions but it will first be negative and change to positive until it reaches an equilibrium position.
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@& 49 N tends to accelerate the system in one direction, 58.8 N in the other. The net force is the difference between these forces.*@
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:
a = 9.8m/sec^2
vf = v0 + a'dt
= 1.8m/sec + 9.8m/sec^2(1 sec)
=11.6m/sec
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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:
During the first second the system will slow down since the direction it is traveling in 'unnatural' so to speak. It is trying to get to a position that will serve as an equilibrium position. During the first second velocity and acceleration are in opposite directions since it is fighting against the normal, resting position.
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@& You should rework this one based on my notes, and be sure to submit this question using the form for this question.*@