1. NEWTON'S
LAWS OF MOTION
2nd Law
1st Law
3rd Law

2. People DO NOT create laws governing the natural world.
We only identify the principles that exist in the physical world and name them for reference!!

3. What makes objects move?
What makes them change their motion?

4. Force Force – a push or a pull
Contact Force – when 2 objects must be touching to exert forces on each other
Friction Pushing or kicking a ball
Long-Range Force – a force that is exerted without the objects having to touch
Gravity Magnetism Nuclear force

5. COMBINING FORCES
Net force – combination of all forces acting on an object
Balanced Forces – 2 or more forces acting on an object cancel each other – they do NOT change the motion of the object (Net Force = 0)
Unbalanced Forces –forces acting on an object do NOT cancel each other – they DO change the motion of the object (Net Force ≠ 0)

6. balanced force

7. REST
MOTION
UNBALANCED FORCES

8. REST
The state of an object when it is not changing position.
THIS IS RELATIVE!!
Not moving in relation to your immediate surroundings!!!

9. MOTION THIS IS RELATIVE, TOO!!
The state of an object when it is changing position in relation to its surroundings.
THIS IS RELATIVE, TOO!!
When you are sitting on an airplane, you are at rest, but if you get up and walk down the aisle, you are in motion.

10. If you are sitting in a seat on a speeding airplane you would still be considered at rest!
If rest were defined as a total absence of motion, it would not exist in nature.

11. If an object is at REST, it takes an unbalanced force to make it move.
UNBALANCED FORCES
If an object is at REST, it takes an unbalanced force to make it move.
If an object is in MOTION, it takes an unbalanced force to stop it, change its direction from a straight line path, or alter its speed.

12. ANY CHANGE IN AN OBJECT'S
ACCELERATION
ANY CHANGE IN AN OBJECT'S
SPEED OR DIRECTION

13. There is no change in motion therefore no acceleration
Balanced Forces
There is no change in motion therefore no acceleration
Unbalanced Forces
There is a force pushing the book to the RIGHT that is GREATER than the force of FRICTION therefore there is acceleration.

14. Newton’s 1st Law of Motion
INERTIA
Lazy, resistant to change!!!

15. Newton’s 1st Law of Motion
If there is NO net force acting on an object then
An object at rest will remain at rest
An object in motion will remain in motion at constant speed.
Until acted upon by an outside force
The truck stops when it hits the car, the ladder continues moving forward because the force of the car was acting on the truck NOT the ladder.

16. Newton’s 1st Law of Motion
From a standing start the truck moves away very quickly causing the passenger to fall backward
After traveling at some speed the truck suddenly comes to a stop causing the passenger to fall forward.
Force was applied to the truck not the passenger!!!

17. Newton’s 1st Law of Motion
MASS OF AN OBJECT = INERTIA OF AN OBJECT
Less mass = less inertia
(smaller resistance to change)
More mass = more inertia
(greater resistance to change)

18. Newton’s 1st Law of Motion
MASS OF AN OBJECT = INERTIA OF AN OBJECT
INERTIA of an object explains why a magician can pull the tablecloth out from under a set of glasses without having them fall over
The glasses have more inertia than the tablecloth as the force (pull) is applied to the tablecloth.

19. Newton’s 2nd Law of Motion
Force is equal to mass times acceleration
F = ma

20. Newton’s 2nd Law of Motion
Cannon

21. Newton’s 2nd Law of Motion
When the cannon is fired, an explosion propels a cannon ball out the open end of the barrel. It flies to its target. At the same time, the cannon itself is pushed backward a meter or two.
ACTION - work
What happens to the cannon and the ball is determined by Newton’s 2nd Law.

22. m(cannon) a(cannon) = m(ball) a(ball)
F = m(cannon) a(cannon)
F = m(ball) a(ball)
Force (exploding gunpowder) is the same for the two equations, they can be combined and re-written
m(cannon) a(cannon) = m(ball) a(ball)

23. m(cart1) a(cart1) = m(cart2) a(cart2)
Acceleration and Mass
Force – Spring-loaded plunger
m(cart1) a(cart1) = m(cart2) a(cart2)

24. The standard unit of force
NEWTON
The standard unit of force
1 newton = the force required to accelerate a mass of 1 kilogram at 1 meter per second per second

25. 1 kg mass x 1 m/s2 acceleration
1 Newton of Force =
1 kg mass x 1 m/s2 acceleration

26. Newton’s Third Law of Motion
For every action there is an equal and opposite reaction

27. Balloons & Rockets?

28. Balloons & Rockets
Air inside a balloon is compressed by the balloons rubber walls.
The air pushes back so that the inward and outward pressing forces balance.
When the nozzle is released, air escapes through it and the balloon is propelled in the opposite direction.

29. Forces become balanced and unbalanced all the time.
Rocket Flight
Forces become balanced and unbalanced all the time.

30. surface of pad pushes the rocket up gravity tries to pull it down
Apollo 11
Launch pad
Balanced
surface of pad pushes the rocket up
gravity tries to pull it down

31. Thrust from rocket pushes up gravity tries to pull it down
Engines Ignited
Unbalanced
Thrust from rocket pushes up
gravity tries to pull it down
Rocket travels upward
Apollo 11

32. Stops at its highest point Gravity pulls it back to Earth
Rocket in travel – rocket runs out fuel
Unbalanced
Rocket will slow down
Stops at its highest point
Gravity pulls it back to Earth
Apollo 17
Apollo 11

33. Orbiting Satellite

34. Controlling velocity is extremely important for maintaining the circular orbit of the spacecraft
Only an unbalanced force such as friction with gas molecules in orbit or the firing of a rocket engine in the opposite direction slowing down the spacecraft will bring the satellite out of orbit!

35. Vocabulary Reaction force Pressure Fluid Buoyant force Weight Displace
Speed
Velocity
Acceleration
Magnitude
Vector
Inertia
Action force
Friction
Gravity
Balanced forces
Unbalanced forces
Reaction force
Pressure
Fluid
Buoyant force
Weight
Displace
Density
Volume
Archimedes Principle