# Homework Help: Rotation rate of hour hand on clock?

1. Nov 19, 2009

### BioGuy

What is the rotation rate in revolutions per minute of the hour hand of a clock?

a.) 1/(12x60)
b.) 1/24
c.) 1/(24x60)
d.) none of these

I am not too sure how to answer this, i want to say its (a.) because it makes the most sense... ??any suggestions??

2. Nov 19, 2009

### mgb_phys

How many minutes are there in 12hours (the time it takes to go around the clock?)
If you have N minutes/revolution - how do you get to revolutions/minute?

hint - if you are going 10miles/hour, what fraction of an hour does it take to go 1 mile

3. Nov 19, 2009

### BioGuy

there are 720 minutes in 12 hours..

you invert(recipricol) of xmin/rev to get revolutions/min

im still a little lost... :-/ how can we disprove some choices?

4. Nov 19, 2009

### gamer_x_

one of the key differences in your choices are the numbers 12 and 24. What do they represent, and which one is relevant in the case of a full rotation of the hour hand?

5. Nov 19, 2009

### mgb_phys

Exactly so the answer is 1/(12*60) = 1/720 as you said.
You don't need to disprove the others - they are just wrong!