| A | B |
|---|
| elastic force | F = -kx |
| weight | mg |
| sliding/sticking friction | opposes relative motion of surfaces |
| rolling/fluid friction | opposes motion |
| forces are: | vectors |
| k has units | N/m |
| Newton I | If F(net) = 0 then a = 0 |
| Newton II | F(net) = ma |
| F(net) | vector sum of all the forces |
| Normal Reaction | at right angles to surfaces |
| Component of weight down slope | mg sin(theta) |
| Component of weight into slope | mg cos(theta) |
| Newton III | force of action = force of reaction |
| Action-reaction pairs | always act on different bodies |
| During a bounce | Normal reaction>weight |
| In a lift accelerating DOWN | Normal reaction <weight |
| If 'action' = your weight | 'reaction' = force you exert on the earth |
| tension forces | always pull |
| compression forces | always push |
