A modified Atwood machine is at rest. The hanging block has a mass of 3kg. The black on wheels has unknown mass M1. When released the block m2 falls at 5.88m/s^2. If frictional forces are considered so small they are negligible, the block M1 must have a mass of _ kg.

From the figure,

The free-body diagrams for  and  are shown in the figures below. The only forces on the blocks are the upward tension  and the downward gravitational forces  and  . Applying Newton’s second law, we obtain:   

which can be solved to yield 

Substituting the result back, we have 

(a) With  and , the acceleration becomes   

(b) Similarly, the tension in the cord is   

the answer is b, have negligible mass

the area between the graph and the t axis