1. Forces and the Laws of Motion

2. Forces Force is a push or pull on an object. Unit for force:
N or Newton.

3. Balanced 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 resists motion and can cause heat
Lubricants help reduce friction
Types of friction
Sliding
Rolling
Fluid
Static

5. Types of friction Static acts on objects that are not moving
Always acts in opposite direction to applied force
Sliding
Opposes direction of motion as an object slides
Less then static friction
Rolling
Friction that acts on rolling objects
100 to 1000 times less than static and sliding friction
Fluid
Opposes the motion of an object through a fluid
Fluids include gases and liquids
Air resistance – fluid friction acting on an object moving
through the air

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. (unbalanced)
2nd Law: The acceleration of a body depends on the ratio of the acting force to the mass of the body. (unbalanced)
F = m x a
3rd Law: for every action there is an equal and opposite reaction. (balanced)

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

8. 2nd Law of Motion Concept: Acceleration
The forces are unbalanced
Examples: hitting a golf ball gently vs. hard.
F = ma
Answer = _50__ newtons

9. Problem 1
How much force is needed to accelerate a
500.0 kg car at a rate of m/s/s?

10. Problem 2
A 100 N force causes an object to accelerate at
2 m/s/s. What is the mass of the object?

11. Problem 3
A 1.5 kg ball is kicked with a force of 450 N.
What acceleration did the ball receive?

12. 3rd Law of Motion Action/ Reaction
Concept: Action/Reaction of objects
Forces are balanced
Examples: Stationary objects, rockets being launched

13. Laws of motion Interactives
interactives/newtons-laws-of-motion- interactive.htm

14. Motion of a falling object after being
Projectile
Motion
Motion of a falling object after being
given an initial forward velocity
Combination of initial vertical force
and downward force of gravity
Causes object to follow a curved path

15. Gravity and Free Falling Objects
Gravity: The attraction between two objects.
All objects fall at a rate of 9.8 m/s2
Gravity acts between two masses
All masses exert the force of gravity – universal force
Galileo did an experiment at the leaning tower of Pisa in Italy with bowling balls. Both balls fell at the same rate.

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

17. Newton’s Law of Universal Gravitation
Shows that objects are attracted to one another in proportion to their masses and their distances away from the object.

18. 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.

19. Both fall at the same rate due to there being no air.
What about a vacuum?
vac·u·um [ vákyoo əm ]
space empty of matter: a space completely empty of matter but not achievable in practice on Earth
space with all gas removed: a space from which all air or gas has been extracted
emptiness caused by absence: an emptiness caused by somebody or something's absence or removal
Both fall at the same rate due to there being no air.

20. Gravity and Weight Gravi ty Mass – measure of amount of inertia
Weight – force of gravity pulling on an object
Weight is product of mass and acceleration due to gravity ( 9.8 m/s/s)
W = mg
W- weight in newtons
m- mass in kilograms
g- acceleration due to gravity in meters per second squared