# Rotational Motion problem

1. Mar 25, 2015

### J-Fly

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A 61 cm diameter wheel accelerated uniformly about its center from 120 rpm to 280 rpm in 4.0 seconds. Determine the Angular acceleration

So I converted the 120 and 280 rev per min to radians per s with 45238.93 rad/s and 105557.51 rad/s and used them as angular velocity final and initial. then I subtracted the final from the initial and divided it by the time (4 sec)

Equation used angular acceleration (fish) = change in angular velocity/time

Answer gotten: 15 x 103 rad/s2 with sig figs.

on the answer sheet= 4.2 rad/s2

2. Mar 25, 2015

### Staff: Mentor

Can you show your calculations for converting the given rpm values to radians per second? Your values look rather high.

3. Mar 25, 2015

### Aceix

er
There is a problem with your conversion. Note that 1rpm=(2pi*1)/60 rad/s

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