1. WHAT IS A FORCE?
A force is a push or a pull that causes an object to change its motion.
Forces can cause objects to accelerate:
Slow Down
Speed Up
Change Direction

2. Measuring Forces The unit used to measure force is the Newton (N).
One Newton is to equal to the force that would give a mass of 1 kg an acceleration of 1 m/s each second.

3. Net Forces Net force is the overall force acting on an object.
Think about what the word “net” means (not like a fishing net). How can this help you remember what a net force is? (Total)
Forces can be represented by arrows since they are vectors.

4. Force Diagram
A force diagram shows all of the forces acting on an object.

5. Balanced Forces
When forces are balanced they have a net force of zero.
No change in movement.
Net Force = 0 N

6. Unbalanced Forces
When forces are unbalanced the net force is not zero.
Causes movement
Net Force = 5 N to the right

7. Force Vectors Practice #1

8. Force Vectors Practice #2

9. Types of Forces 5 Types of Forces to Know: Friction Gravity Normal
Applied
Tension

10. FRICTION
FRICTION is a force that opposes sliding between two surfaces.
The friction force on an object always points in a direction opposite to the relative motion of the object.
Brakes push against the wheels of a car or a match rubs against a strikepad.

11. GRAVITY GRAVITY pulls objects towards one another.
Airplanes are pulled towards the ground and our planet is pulled towards the sun.

12. Gravity Gravity is what causes objects to have weight.
Mass is the amount of matter in an object.
Weight is the force of gravity acting on an object so it is actually a measure of force.

13. NORMAL
The NORMAL FORCE is a push directed at right angles from the surfaces of the interacting objects.
The ground pushes up against our feet.

14. APPLIED APPLIED FORCES are when one object pushes another.
A batter pushes a baseball with his bat.

15. Tension
Tension force occurs when a non-slack rope, wire, cord or similar device pulls on another object.
A string holds up a kilogram weight or a girl hangs from trapeze rings.

16. Calculating Weight on Earth
Remember weight is the force due to gravity.
Knowing this concept we are able to calculate weight using the acceleration due to gravity on Earth.
What is the acceleration due to gravity on Earth?
9.8 m/s2
Ex. Calculate the weight of a person on Earth with a mass of 58 kg.
W = ma = (58 kg)(9.8 m/s2) = N