#$&*
Phy 121
Your 'cq_1_12.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
** **
Masses of 5 kg and 6 kg are suspended from opposite sides of a light frictionless pulley and are released.
What will be the net force on the 2-mass system and what will be the magnitude and direction of its acceleration?
answer/question/discussion: ->->->->->->->->->->->-> :
The first mass of 5 kg will have a Force of 9.8 m/s^2 * 5 kg = 49 N
The second mass of 6 kg will have a Force of 9.8 m/s^2 * 6 kg = 58.8 N
The mass of 5 kg is working against the mass of 6 kg so its Force would be -49N
Fnet = -49 N + 58.8 N = 9.8 N
a = Fnet / m = 9.8 N / 11 kg = .891 m/s^2
This acceleration is in the direction of the 6 kg mass.
#$&*
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 am drawing blanks alot in these first few assignments. In this case the 5 kg mass is first working against the 6 kg by pulling the system towards the 5 kg mass, however after the initial velocity dissipates the 6 kg mass will then begin to be the dominant work force of the system. I do not however understand how to calculate this.
The known forces acting on the system are gravity on the 5 kg mass (-49 N), gravity on the 6 kg mass (58.8 N) and the initial velocity push of 1.8 m/s on the 5 kg mass (? N). I know that the KE here is .5 * 5 kg * 1.8 m/s = 4.5 (I am not sure of these units, Joules maybe) but I do not know how to turn this KE into Force of Work done on the system.
Your intuition is correct, and you'll have no problem with this once you choose your positive direction. The discussion at the link will help straighten you out.
#$&*
During the first second, are the velocity and acceleration of the system in the same direction or in opposite directions, and does the system slow down or speed up?
answer/question/discussion: ->->->->->->->->->->->-> :
Once again I can describe what I think would happen, but I simply do not know what to do. The initial second we will see more work being done in the direction of the 5 kg mass with an initial velocity push. However the more time gravity has to pull on the 6 kg mass then the more and more the 5 kg mass will slow down and the system will shift towards the 6 kg mass. So the system starts towards the 5 kg, slows down, stops for a moment, then slowly shifts towards the 6 kg mass at an increasing rate.
#$&*
** **
** **
Check the discussion at the link, and submit a revision if you have further questions.
&#See any notes I might have inserted into your document, and before looking at the link below see if you can modify your solutions. If there are no notes, this does not mean that your solution is completely correct.
Then please compare your old and new solutions with the expanded discussion at the link
Solution
Self-critique your solutions, if this is necessary, according to the usual criteria. Insert any revisions, questions, etc. into a copy of this posted document. Mark any insertions with &&&& so they can be easily identified.If your solution is completely consistent with the given solution, you need do nothing further with this problem. &#