1. Forces
Physics- Ms. Jeffrey

2. The meaning of force
Force- A push or a pull on an object resulting from an interaction with another object.
Forces only exist as a result of an interaction.
The unit of Force is the Newton [N]
Force is a vector quantity
Two types of forces
Contact forces
Action-at-distance forces

3. Contact forces
Contact forces- result when the two interacting objects are physically contacting each other.
Examples
Frictional Force
Tension Force
Normal Force
Air Resistance Force
Spring Force
Applied Force

4. Friction Force
Force exerted by a surface as an object moves across it.
This force opposes the motion of an object.
Two types:
Static
The frictional force that keeps an object at rest
This force must be overcome to get an object to start moving.
Kinetic
The frictional force that slows an object down
The object is already in motion.

5. Tension force
The force that is transmitted through a rope or cable when it is pulled tight by forces acting in opposite directions.
Pulling force

6. Normal force Support force exerted on an object by a surface
If two objects are not in contact, they cannot exert a normal force on each other.
What would happen if there was no normal force?

7. Air resistance force
Special type of frictional force that acts on objects as they travel in air
Opposes the motion of an object (just as friction does on a surface)
Pushes against a moving object
What are some examples of air resistance?

8. Spring force
Force exerted by a compressed or stretched spring upon an object
Restores the object back to rest, or equilibrium

9. Applied Force
A force that is applied to an object by a person, or another object
Pushing or pulling an object
What are some examples of applied forces?

10. Action-at-a-distance forces
Action-at-a-distance forces- result when two interacting objects are not in physical contact.
They still apply a push or pull on other objects
Examples
Gravitational Force
Magnetic Force
Electrical Force

11. Gravitational force
The force with which a massive object attracts another object towards itself
Which direction does gravity act?
The force of gravity is equal to the weight of an object
To find the force of gravity, use the equation: Fg = m*g
Where g= -9.8 m/s2 and m=mass of object
MASS AND WEIGHT ARE NOT THE SAME
Mass is the amount of matter an object has
Weight is related to the pull of the Earth on an object
If an object’s mass is 2 kg, what will it’s mass be on the moon?