1. Forces and the Laws

2. Forces N or Newton. Force is a push or pull on an object.
Can cause a resting object to move or it can accelerate a moving object by changing the object’s speed or directions
Unit for force:
N or Newton.

3. Balanced forces: Unbalanced forces:
Where there are two forces that counteract each other and result in no movement (EQUAL)
Unbalanced forces:
One force is greater than the other force. (UNEQUAL)

4. Friction A force that resist motion and can cause heat
Lubricant help reduce friction
Types of friction
Static
Sliding
Rolling
Fluid

5. Types of Friction
Static—is the friction force that acts on objects that are not moving
Sliding—is the force that opposes the direction of motion of an object as it slides over a surface
Rolling—the friction force that acts on rolling objects
Fluid—opposed the motion of an object through a fluid
Fluids= water and mixture of gases
Fluid friction action on an object moving through the air is known as air resistance

6. Newton’s Laws of Motion
1st Law: Objects at rest remain at rest, or objects in motion remain in motion unless acted upon by a force.
2nd Law: The acceleration of a body depends on the ratio of the acting force to the mass of the body.
3rd Law: for every action there is an equal and opposite reaction.

7. 1st Law of Motion (Law of Inertia)
Inertia: force that is resistant to the direction of the motion
Unbalanced forces
Examples: Inertia belts (seat belts)

8. 2nd Law of Motion Concept: Acceleration Unbalanced forces
Examples: hitting a golf ball gently vs. hard.
Answer = ___ newtons

9. 2nd Law of Motion Formula:
Force=mass x acceleration
F=ma
How much force is needed to accelerate a kg car at a rate of m/s/s?
A 100 N causes an object to accelerate at 2 m/s/s. What is the mass of the object?
A 1.5 kg ball is kicked with a force of 450 N. What acceleration did the ball receive?

10. 3rd Law of Motion Action/ Reaction
Concept: Action/Reaction of objects
Balanced forces
Examples: Stationary objects, rockets being launched

11. Gravity and Free Falling Objects
Gravity: is a force that acts between two masses
Acts downward towards the center of the Earth
All objects fall at a rate of 9.8 m/s/s
Galileo did an experiment at the leaning tower of Pisa in Italy with bowling balls. Both balls fell at the same rate.
Galileo's experiment at the Tower of Pisa

12. Projectile Motion
The motion of a falling object after it is given an initial forward velocity

13. Air Resistance
Force that slows down falling objects due to the atmosphere and surface area of the object.

14. Newton’s Law of Universal Gravitation
Shows that objects are attracted to one another by their mass and their distance away from the object.

15. Feather vs. Rock
Earth: feather would float down (air resistance) while the rock would drop at 9.8 m/s/s
Moon: feather and rock would drop at same rate due to no atmosphere and air resistance.

16. What about a vacuum?
Both fall at the same rate due to no air being in the jar.

17. Gravity and Weight Weight—is the force of gravity acting on an object
Expressed as Fg
Formula
Weight=mass x acceleration due to gravity (g)
Fg=mg
g=9.8 m/s/s