# Homework Help: Formula of power

1. Jul 31, 2016

1. The problem statement, all variables and given/known data
i was told that Power = torque x (angular velocity)

2. Relevant equations

3. The attempt at a solution
I found that power has unit of Nm/s,
torque x (angular velocity) has unit of Nm(rad/s), is the formula given wrong?

2. Jul 31, 2016

### haruspex

Angles do not have a dimension in the way that mass, time, etc. do.
Consider e.g. that a circular arc of radius r and angle θ has length rθ.
Nevertheless, they do have units, and the unit "radian" is chosen in such a way that you do not need to include a constant in the rθ formula. It turns out that this also means you do not need a constant in the power formula if radians are used in the angular velocity.

3. Aug 4, 2016

### rude man

Or, angles are dimensionless.