phy 121
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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 mass:
F = 5kg * 9.8m/s^2
F = 49 Newtons
6kg mass:
F = 6kg * 9.8 m/s^2
F = 58.8 Newtons
Total net force of 2-mass system:
49 Newtons + 58.8 Newtons = 107.8 Newtons
The magnitude will be equal and the direction of acceleration for the 5kg mass is up and the direction of acceleration for the 6kg mass is down.
• 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: ->->->->->->->->->->->-> :
I don’t understand how the 5kg object can be descending, shouldn’t it be ascending?
Not if the system was given a push to start it in the opposite direction.
If you throw a ball up into the air its acceleration is down but its initial velocity is up. That situation eventually brings it to rest, after which it starts moving (and speeding up) in the downward direction.
Very similar situation here.
• 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: ->->->->->->->->->->->-> :
velocity and acceleration would be in opposite directions, the system will slow down.
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15 min.
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