PHY 201
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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: ->->->->->->->->->->->-> :
The 5kg is suspended on one side and the 6 kg on the other. So, first I need to find the force on each side: 5 kg * 9.8 m/s^2 = 49 N, and 6 kg * 9.8 m/s^2 = 58.8 N, which the net force is: 58.8 N + 49 N = 107.8 N. The force that is going to be positive is the 58.8 N. So, the net force now is: +58.8 N + -49 N = +9.8 N. The total mass of the system is 11 kg and the net force is 9.8 N, then the acceleration will be the net force divided by the mass: 9.8 N / 11 kg = +.89 m/s^2.
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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: ->->->->->->->->->->->-> :
Since the direction of the 6 kg is positive, the direction of the 5 kg is going to be negative. So, it is descending at -1.8 m/s. The acceleration of the whole system is +.89 m/s^2. I am not sure how to get the speed of the object 1 second later????????
you have the acceleration, which is the rate at which velocity changes with respect to clock time
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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 is going in the negative direction, because the direction of the 6 kg object is positive, so the direction of the 5 kg is negative. The acceleration of the object negative as well, so both are going in the same direction. The system will slow down because the object is being pushed in the 5 kg direction and will eventually go to a stopping point and go in the positive direction.
you have given a positive acceleraton and a negative initial velocity; according to your quantities they are not in the same direction
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45 minutes
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very good start; see my notes
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Solution
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