In the diagram, the velocity of pulley C is the same as the velocity of m2, so m2 is now drawn as the axle of pulley C. Note that the coordinates yi are all negative. Since the pulleys are frictionless and massless, they exert no forces on the string along its length, so the tension T in the string will be the same throughout. The forces exerted on the pulleys by the string are indicated by the red arrows in the diagram. The equations of motion for m1 and the two pulleys are thus
Pulley B:
[Eq. 1]
Mass m1:
[Eq. 2]
Pulley C:
[Eq....
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