1. Newton’s Laws

2. Forces A force is a push or pull on an object.
Forces are vectors - have magnitude and direction.
Multiple forces applied to an object is the same as the effect of a single force equal to the vector sum of the forces applied.

3. Newton’s First Law
An object at rest will remain at rest and an object in motion will continue in motion in a straight line at constant velocity unless the object experiences an external force.
Often called the law of inertia.

4. Newton’s First Law
Inertia is the resistance of an object to changes in motion.
The measure of the inertia of an object is mass.
The more mass an object has the greater the resistance to changes in motion.
Demo: We use this principle to determine relative weights of objects. Hold two objects in your hands and move them back and forth. You can easily tell which one is heavier.

5. Inertia at Work

8. Newton's Second Law
The net force acting on an object equals the product of the mass and the acceleration of the object.
The direction of the force is the same as that of the acceleration.

9. Newton's Second Law

10. Newton's Second Law

11. Force = mass x acceleration
F=ma

12. Force = mass x acceleration F=ma

13. Weight
Weight (W) is the force of Earth’s gravitational attraction to a body.
The acceleration is the acceleration due to gravity, g = 9.8 m/s2 or 32 ft/s2
The magnitude of the gravitational force acting on an object of mass (m) near the Earth’s surface is called the weight of the object
W= mg

14. Newton’s Third Law
When one object exerts a force on another object, the second object exerts a force of the same magnitude but in the opposite direction on first.
Often stated as “For every action there is an equal and opposite reaction.

15. The action and reaction forces act on different objects
The action force is the balloon pushing the air out.
The reaction force is the air pushing the balloon forward.