# Help needed with a problem on finding max radius

1. Nov 2, 2004

### akane

ok, here we go. I got this problem and i cant figure out how to solve it.

A pulsar is a celestial object that emits light in short bursts. A pulsar in the Crab Nebula flashes at a rate of 30 time/s. Suppose the light pulses are caused by the rotation of a spherical object that emits light from a pair of diametrically opposed "flashlights" on it equator. What is the maximum radius of the pulsar if no part of its surface can move faster than the speed of light
(3.00 x 10 to the 8th m/s)?

Thanks a lot! I appreciate your help-

Akane

2. Nov 2, 2004

3. Nov 2, 2004

### akane

anyone?> i tried solving it myself but no luck

4. Nov 2, 2004

### Staff: Mentor

What have you tried?

Here are a few hints:

Since there are two light sources, what rotation rate must the object have? What angular velocity?
What's the relationship between surface speed and angular velocity?

5. Nov 3, 2004

### akane

i am sorry but i still don't understand this chapter. If you could give me some more hints i would really appreciate it

6. Nov 3, 2004

### Staff: Mentor

The relationship between the surface speed at the equator and the angular velocity $\omega$ (which is measured in radians/sec) is $v = \omega r$.

7. Nov 4, 2004

### akane

thank you very much! it helped me figure out the problem. :yuck: it was not that bad-