# Homework Help: Finding units for power via Dimensional Analysis? Makes no sense

1. Jul 30, 2011

### Elysian

1. The problem statement, all variables and given/known data

"Power is the rate at which work is performed.

Power is signified by W for watts.

Power is also the amount of energy transmitted in a unit of time (s).

Energy is measured in joules. Joules have the units of Newton∙meters.

A Newton is a unit of force. It is equal to the amount of force required to give a 1 kilogram mass and acceleration of one meter per second squared."

Using the aforementioned information, determine the units for power by completing a dimensional analysis.

2. Relevant equations
Down

3. The attempt at a solution

Ok so I know that the units for power are Joules/seconds.. How would you go about getting this by dimensional analysis at all?

So I've done

P = J/s

Power (P) = Work (W)/time (t)
P is in Watts (W)
Watts is J/s

Not sure at all what to do, this is worded so weirdly.. If anyone could help me see what exactly to do, that'd be appreciated.

2. Jul 30, 2011

### hubewa

Currently, you have done this question by working backwards. You were pretty much there.

The unit for Force is Newtons

Work = force * distance. Hence, the units for work is Newtons * distance (Nm) which is equivalent to Joules.

Now, reapply this to what you've already done and you're pretty much there.

3. Jul 30, 2011

### Clever-Name

It might be asking you to get strictly down to units of kg, m, and s.