Saturday
August 23, 2014

Homework Help: Physics

Posted by Sarah on Thursday, June 25, 2009 at 11:59pm.

A small block on a frictionless horizontal surface has a mass of 2.5010−2 Kg. It is attached to a massless cord passing through a hole in the surface. The block is originally revolving at a distance of 0.300 m from the hole with an angular speed of 1.75 rad/s. The cord is then pulled from below, shortening the radius of the circle in which the block revolves to 0.150 m. You may treat the block as a particle.
A) is angular momentum conserved?
B) What is the new angular speed?
C) Find the change in kinetic energy of the block.
D) how much work was done in pulling the cord.

For C i have:
KEf=(1/2)(2.5*10^-2)(.150*7)^2
=.01378125

KEi=(1/2)(2.5*10^-2)(.300*1.75)^2
=.0034453125

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