# Question #f5fed

Jan 23, 2018

Just a force tha makes something spin because it (the ‘line of action of the force’ in posh terms) doesn’t pass through the central axis.

#### Explanation:

A moment is what you do whenever you twist or spin something. You apply an off-centre force to do that and that is a moment.

Mathematically is is defined as $M = F \times d$ measured in Nm (pronounced “Newton-metres”) and explains why spanners have long handles (increasing the distance increases the moment you apply) and why you can hold a door open more easily the further your hand is from the hinge (the pivot.)

The most common example when learning this is the uneven weights of children using a see-saw (“teeter-totter” in the US I think) requiring them to sit at different distances from the pivot or fulcrum.

OK now?