What are moments?
A moment is the quantity (Nm) which tells us the turning effect of a force (N). To calculate a moment, you simply need to know the size of the force and its distance from the pivot.
This can be written as the following equation:
Moments and angular forces
Forces acting at an angle to a pivot need to be re-calculated so only their vertical component is present, this can be done using some simple trigonometry.
Simply use the following to calculate the vertical force:
The sinθ added to the equation acts as a ratio-type variable to the equation, reducing the force as the angle is altered. You can imagine that a force acting at an angle of 90° would result in no force affecting the pivot vertically, this can be a useful piece of information when you come to check your answers later in the exam.
Real-world examples of moments
Think about the application of moments in the real world, here are some examples:
- A door and door handle
- A playground seesaw
- Shop sign hanging from a wall
- Books on a bookshelf
- A car on a bridge
