## Stability

### Gap-fill exercise

Fill in all the gaps, then press "Check" to check your answers. Use the "Hint" button to get a free letter if an answer is giving you trouble. You can also click on the "[?]" button to get a clue. Note that you will lose points if you ask for hints or clues!

Finding the centre of mass

1. Hang the piece of card from one point near the edge and suspend a from the same point.
2. Mark the position of the line with two crosses and draw a line through them
3. Repeat from one or two other points. The lines will cross at the .
4. The shape will on a point at the Centre of Mass.

Stable and Unstable Equilibrium

Stable - A body will return to its position if it is displaced slightly, because its centre of mass is directly below the point of support e.g. hanging basket:

Unstable – the body does not to its equilibrium position if displaced slightly eg plank on a roller

Objects at an angle

An object will if it is pushed, and it will if the centre of mass is beyond the point or points of contact with the ground

A body is more if its centre of mass is low

Conditions for Equilibrium

1. The resultant force is .

2. The principle of moments must apply (the net moment about a point is zero)
– in other words, the moments of the forces about a point will .