(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A student of mass m=40 kg is standing on the edge of a uniform, frictionless turntable, with diameter d = 5m and mass M=400 kg. The student and the turntable are initially rotating counterclockwise together about a fixed axis through the center of the turntable with an angular velocity ofw_{i}= 2 rev/min.

The student now start to walk around the edge of the turntable so that the turntable comes to rest. What is the resulting speed v of the student relative to someone standing next to the turntable? In what direction is the student walking, clockwise or counter clockwise?

2. Relevant equations

conversion of rev/min to rad/s = rev/min * 1min/60s * 2(pi)/1rev

Conservation of angular momentum:

L_{i}= L_{f}

3. The attempt at a solution

(I_{turntable}+ I_{student})w_{i}= I_{turntable}(w_{f}) + I_{student}(w_{final for student})

( (1/2)(400)(2.5)^{2}+ (40)(2.5)^{2}) (.209) = ( (1/2)(400)(2.5)^{2}) (0) + ( (40)(2.5)^{2})w_{f}

Solve forw_{f}and I got 1.254 rad/s

Then use v = (r)w_{f}= (2.5)(1.254) = 3.135 m/s

The student is walking in the counterclockwise direction

Can someone let me know if this is right? I thought it was too easy for a 30 point question

**Physics Forums | Science Articles, Homework Help, Discussion**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Student on a Turntable

**Physics Forums | Science Articles, Homework Help, Discussion**