Phy 201
Your 'cq_1_12.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
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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:
First we take the 5kg*9.8m/s^2=49newtons and 6kg*9.8m/s^2=58.8newtons.We will make the
heavier mass the direction of motion. We need to find the Fnet by taking
58.8newtons-49newtons=9.8newtonsKnow we now the Fnet we can find a.
a=Fnet/m,9.8newtons/11kg=.9m/s^2. So the acceleration will be in the direction of the 6kg
mass at a speed of .9m/s^2
Good, but that's an acceleration, not a speed.
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:
If you are going in the opposite direction of motion then the acceleration should be
-.9m/s^2 and if you are travling at -1.8m/s then you will have a speed of-.9m/s
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:
They are both travling in the same direction and the velocity is slowing but the
acceleration is not and will not change until it starts in the other direction
As you correctly say in your previous result, relative to your chosen positive direction the initial velocity would be negative. The acceleration is, as you seem to understand, positive.
This results in a positive change in velocity, so that your initial velocity was -1.8 m/s and your final velocity -.9 m/s.
The acceleration and the initial velocity are therefore in opposite directions.
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25minutes
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Good work on most of the problem. However I'm not sure about your answers to the last question.
See my notes and be sure you understand, as I believe you will. If not, be sure ask.