Laws of Motion
Given all the observations of motion, Newton found 3 laws which summarized and codified them:
N1: Inertia
- A body in straight line motion (or rest) continues unless an external force acts on it.
- Focusses attention on forces present
N2: Acceleration
- the acceleration a (the change from st. line motion or rest)
- is proportional to the applied force F
- and inversely proportional to the object mass m
- hence a = F/m, or F = ma
- definite, exact, mathematical interrelationship
- Must distinguish between velocity and speed
- speed = (distance travelled) per (unit time), i.e 60 mph
- velocity is speed plus direction