Two masses are connected by a light string passing over a light frictionless pul

Question

Two masses are connected by a light string passing over a light frictionless pulley as shown on Figure. The M2= 6.6 kg mass is released from rest at height h = 2.0 m . We are given that M1= 2.8 kg.  Use 10 N/kg for g. Show work !

a) What is in Joules, the initial gravitational potential energy of the system relative to the ground?

b) What is in Joules, the final (the instant M2 touches the ground) gravitational potential energy of the system relative to the ground?

c) What is in Joules, the final (the instant M2 touches the ground) kinetic energy of the system?

d) What is in m/s the speed of M1 just as M2 hits the ground?

Explanation / Answer

a) initial gravitational potential energy of the system relative to the ground= M2*g*H = 129.492 Joule

b) final gravitational potential energy of the system relative to the ground=M1*g*H= 54.936 Joule

c) kinetic energy of the system= 129.492-54.936 = 74.556 Joule

d)

Change in P.E = 0.5*(m1+m2)*V2

speed of M1 just as M2 hits the ground= 3.9828 m/sec

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