# Circular motions

1. Jun 26, 2004

### akatsafa

I haven't worked with circular motions yet but i have these questions for lab. Could someone please help?

A group of students observes that a wooden block o mass o.29kg on a string makes 15 rotations in 23.5 seconds at a radius of 0.70 meters. (a) the blocks tangential velocity is.. (b) the blocks angular velocity is..

I tried using the equation v= 2pi r/T but that's not working. With that I got 0.87m/s but it's not right. What equations should I use for these?

2. Jun 26, 2004

### Corneo

Hi, I think I got it but do check my work.

First we calculate the $$\omega$$ and then we use it to find $$v$$.

$$\omega = \frac {15 \text{rev}}{23.5 \text{s}} \times \frac {2\pi}{1 \text{rev}} = 4.01 \text{rad/s}$$

Using $$v=r \omega$$ we get $$v=2.807 \text{m/s}$$

Last edited: Jun 26, 2004
3. Jun 26, 2004

### akatsafa

thank you...that's right. I wasn't accounting for the 15 revolutions. I was just using one revolution.