Moment formula

We can calculate the moment (M) using the formula:

M = F \times d

Where:

• M is the moment
• %F$ is the force
• d is the perpendicular distance from the centre

Units

We can calculate a moment using \text{force}\times\text{[[distance]]}.

• Force is measured in newtons
• Perpendicular distance is measured in metres

So if we do \text{newton}\times\text{metre}, we get the unit for moments to be the Newton-Metre!

Example calculations

A force of 5N is applied 10m away from a pivot. Calculate the moment.

• F=5
• d=10
• M=Fd
• $M=(5)(10)%
• M=50\space Nm

A force of 5N is applied 2m away from the pivot. Another force, F, is applied 5m away from the pivot. The overall moment is 25Nm. Calculate F.

• Total moment = sum of all moments
• M_1=5\times2=10
• M_2=M_{total}-M_1
• M_2=25-10
• M_2=15
• M_2=F\times5=15
• F=3N

A person is capable of exerting a force of 200N onto a plank of wood. If the moment needed to snap the wood is 1200Nm, how far away does the person need to press down on the plank of wood?

• M=Fd
• d=\frac MF
• d=\frac{1200}{200}
• d=6m