October 7, 2015

Homework Help: Physics

Posted by Luke on Monday, March 24, 2014 at 2:56pm.

A small block on a frictionless surface has a mass
of 70 g. It is attached to a massless string passing
through a hole in a horizontal surface (see diagram).
The block is originally rotating in a circle of radius 45
cm with angular speed 0.80 rad/s. The string is then
pulled from below until the radius of the circle is 25
cm. You may treat the block as a point particle.

(a) Is the angular momentum of the block conserved?
Why or why not? (b) What is the final angular speed?
(c) What are the initial and final tensions in the string?
(d) What was the change in kinetic energy of the block?
(e) How much work was done in pulling the string?

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