Dynamics

Freeform

Boxed

Free Response Problems

A $45$ kg boy stands on $30$ kg platform suspended by a rope passing over a stationary pulley that is free to rotate. The other end of the rope is held by the boy. The masses of the rope and pulley are negligible. Ignore the friction in the pulley.

a$.$ If the rope and the boy are at rest, what is the tension in the rope?

The boy now pulls on the rope so that the acceleration of the boy and the platform is $1\mathrm{.}5\frac{m}{s^2}$ upward.

b$.$ What is the tension force in the rope under these new conditions?

c$.$ Under these conditions, what is the force exerted by the platform on the boy?

After a short time, the boy and the platform reach and sustain an upward velocity of $0\mathrm{.}3\frac{m}{s}.$

d$.$ Determine the power output of the boy required to sustain this velocity.