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1.)The figure on the right shows a system of two masses connected by a string. A

ID: 1873097 • Letter: 1

Question

1.)The figure on the right shows a system of two masses connected by a string. As m falls a distance h, M accelerates up the plane. The coefficient of friction between M and the inclined plane is . Show in detail that the change of kinetic energy is h; given by AK=2(m+M)[vr-r]. Do not assume that system starts at rest What is the change in potential energy on the system after the m has fallen a distance h? What is the work done by friction on the system? Please explain and show all work. Thank you!

Explanation / Answer

change in PE of m = - m g h

for M, = M g (h sin(theta))


change in PE = g h ( M sin(theta) - m )


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friction force, f = u N = u M g cos(theta)

Work done = - f.h

= - u M g h cos(theta)


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total work done = work done by gravity+ work done by friction

= - change in PE + Work done by friction

= m gh - M g h sin(theta) - u M g h cos(theta)


= g h ( m - M sin(theta) - u M cos(theta) )

and net work done = changein KE


so delta(K) = g h ( m - M sin(theta) - u M cos(theta) )