Question

Review. An object with a mass of m 5 5.10 kg is
attached to the free end of a light string wrapped around
a reel of radius R 5 0.250 m and mass M 5 3.00 kg. The
reel is a solid disk, free to rotate in a vertical plane about
the horizontal axis passing through its center as shown in
Figure P10.51. The suspended object is released from rest
6.00 m above the floor. Determine (a) the tension in the
string, (b) the acceleration of the object, and (c) the speed
with which the object hits the floor. (d) Verify your answer
to part (c) by using the isolated system (energy) model.

Answer 1

Look at energy.

Intial gravational energy=mass*g*h

rotaltional energy=1/2 I w^2=1/2 I(v/r)^2
(look up the moment of inertia for a solid disk I)

rotational energy+1/2 mv^2=Initial GPE
solve for v when it hits the floor (c) this will verify the following.

a) net force=torque=momentI*angularacceleration
= I*tangential acceleration/r=I*a/r

and net force=mg-ma

mg-ma=I a/r solve for a, (b), then solve for tension (mg-ma)

Now
a)

Answer 2

wr2