Understanding Newton's Laws of Motion

1. Newton’s Laws of Motion How can we describe how objects move?

2. Newton’s 1st Law of Motion The law of BALANCED FORCES • Objects at rest tend to stay at rest. • Objects in motion tend to stay in motion. • An object’s motion does not change if the forces do not change. • This is known as inertia.

4. Newton’s 1st Law of Motion • When you consider an object, think about the system of forces acting on it. • A force is a push or a pull acting on an object. • Don’t forget about gravity and friction!

5. Newton’s 2nd Law of Motion The law of UNBALANCED FORCES • IF the forces acting on an object are unbalanced, the object’s motion (velocity) will change. (The object will accelerate.) • The change is in proportion to and in the same direction as the unbalanced force.

7. Newton’s 2nd Law of Motion • Mathematically, f = ma • The unit for force is a newton. • N = kgm/s2 • Mass is a measure of inertia. • Weight is a measure of the force of gravity.

8. Newton’s 3rd Law of Motion The law of ACTION AND REACTION • For every action there is an equal and opposite reaction. • Think of the objects and forces as a system. • Actions/reactions come in pairs. Their FORCES are equal and opposite, but the MASSES and ACCELERATIONS are not. • Remember, f = ma!

9. Newton’s 3rd Law of Motion • f = ma (units are kgm/s2 or N) • If two equal masses are acted on withdifferentforces, the resulting accelerations will be in proportion to the forces. f a f a

10. Newton’s 3rd Law of Motion • f = ma (units are kgm/s2 or N) • If two masses are acted on with equal forces, the resulting acceleration will depend on each of their masses. f a f a