1. Balanced and Unbalanced Forces

2. Vocabulary
Vocabulary Chart
Vocabulary Chart with Definitions

3. Isaac Newton Sir Isaac Newton was a great scientist and mathematician.
Isaac Newton was the first person to hypothesize that the force that pulls an apple to the ground also pulls the moon toward Earth, keeping it in orbit.
He developed three laws of motion that we still know to be true today *

4. Newton’s Laws of Motion
An object in motion tends to stay in motion and an object at rest tends to stay at rest unless acted upon by an unbalanced force.
Force equals mass times acceleration (F = ma).
For every action there is an equal and opposite reaction.

5. Force A force is a push or a pull.
Force gives an object the energy to move, stop moving, or change direction.
When you write with a pen you exert a force. When you peddle your bike, blow your nose, turn on a faucet, chew your gum, or swimming in a pool, you are exerting forces on other objects.
We would never be able to move without exerting forces on things.
                      
       
             *

6. Newton’s First Law of Motion
An object at rest will remain at rest unless acted on by an unbalanced (unequal) force.
An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced (unequal) force.
This law is often called "the law of inertia". *

7. What is meant by unbalanced force?
If the forces on an object are equal and opposite, they are said to be balanced, and the object experiences no change in motion. If they are not equal and opposite, then the forces are unbalanced and the motion of the object changes.

8. Some Examples from Real Life
A soccer ball is sitting at rest. It takes an unbalanced force of a kick to change its motion.
Two teams are playing tug of war. They are both exerting equal force on the rope in opposite directions. This balanced force results in no change of motion.

9. Law of Inertia
Inertia- the tendency of an object to resist a change in motion.
This law is the same reason why you should always wear your seatbelt. *

10. Inertia
Newton’s First Law says that objects do not accelerate spontaneously, they need an outside force to move.
This property of matter, which causes objects to resist acceleration, has been named “inertia”.
Newton’s First Law is often called the Law of Inertia. *

11. Inertia at Work
Car crash with and without seatbelts and air bags *

12. Examples of the Law of Inertia
index card/penny example
magician's trick of pulling a tablecloth out from under dishes on a table.
when riding a horse, the horse suddenly stops and you fly over its head
car turns left and you appear to slide to the right
football player running with the ball
Inertia in action – video clip *

13. More Examples from Real Life
A powerful locomotive begins to pull a long line of boxcars that were sitting at rest. Since the boxcars are so massive, they have a great deal of inertia and it takes a large force to change their motion. Once they are moving, it takes a large force to stop them.
On your way to school, a bug flies into your windshield. Since the bug is so small, it has very little inertia and exerts a very small force on your car (so small that you don’t even feel it).

14. If objects in motion tend to stay in motion, why don’t moving objects keep moving forever?
Things don’t keep moving forever because there’s almost always an unbalanced force acting upon it.
A book sliding across a table slows down and stops because of the force of friction.
If you throw a ball upwards it will eventually slow down and fall because of the force of gravity.

15. Friction
Friction is a force that opposes motion. Friction acts in a direction opposite to the objects direction in motion.
Without friction, the object would continue to move at a constant speed forever.
Example: sliding friction. This is when two surfaces slide one over the other. A snowboarder slides over the snow covered slopes using sliding friction every day. *

16. Friction The amount of friction depends on:
The condition (smoothness/roughness) of the surfaces
The normal force between the surfaces

17. Gravity Newton was the first person to seriously study gravity
Gravity is a force that attracts all objects toward each other.
The force of gravity is measured in units called Newtons (N).
What is gravity? *

18. Gravity
The strength of gravity between two objects depends on two factors:
1. masses of the objects (If mass increases, force also increases)
2. distance between the objects (If distance increases, force decreases) *

19. Gravity *

20. Gravity The greater the mass, the greater the force
The greater the distance, the less the force
Acceleration due to gravity = 9.8 m/s/s or 9.8 m/s2 *

21. Mass vs. Weight Mass- is the amount of matter in an object
Weight- is the force of gravity on an object
The greater the mass the greater the force (weight)
Weightlessness – free from the effects of gravity
Mass vs. Weight *

22. Newton’s 1st Law activities
Wacky washers and penny lab

23. How does Friction work?
In today’s experiment, we will see just how friction effect our movements in everyday life.
Teacher Notes

24. Force equals mass times acceleration.
Newton’s Second Law
Force equals mass times acceleration.
F = ma
Acceleration: a measurement of how quickly an object is changing speed.

25. Newton’s Second Law 70 Newtons Force = Mass x Acceleration
Force is measured in Newtons
ACCELERATION of GRAVITY(Earth) = 9.8 m/s2
Weight (force) = mass x gravity (Earth)
Moon’s gravity is 1/6 of the Earth’s
If you weigh 420 Newtons on earth, what will you weigh on the Moon?
70 Newtons
If your mass is 41.5Kg on Earth what is your mass on the Moon?

26. WEIGHT is a measure of the force of ________ on the mass of an object
Newton’s Second Law
WEIGHT is a measure of the force of ________ on the mass of an object
measured in __________
gravity
Newtons *

27. Newton’s Second Law One rock weighs 5 Newtons.
The other rock weighs 0.5
Newtons. How much more
force will be required to
accelerate the first rock
at the same rate as the second rock?
Ten times as much

28. What does F = ma say?
F = ma basically means that the force of an object comes from its mass and its acceleration.
Something very massive (high mass) that’s changing speed very slowly (low acceleration), like a glacier, can still have great force.
Something very small (low mass) that’s changing speed very quickly (high acceleration), like a bullet, can still have a great force. Something very small changing speed very slowly will have a very weak force.

29. Working with Newton’s 2nd
Complete the graphing Newton’s second law activity sheet

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

31. Newton’s 3rd Law
For every action there is an equal and opposite reaction.
Book to
earth
Table to
book

32. What does this mean?
For every force acting on an object, there is an equal force acting in the opposite direction. Right now, gravity is pulling you down in your seat, but Newton’s Third Law says your seat is pushing up against you with equal force. This is why you are not moving. There is a balanced force acting on you– gravity pulling down, your seat pushing up.

33. Think about it . . .
What happens if you are standing on a skateboard or a slippery floor and push against a wall? You slide in the opposite direction (away from the wall), because you pushed on the wall but the wall pushed back on you with equal and opposite force.
Why does it hurt so much when you stub your toe? When your toe exerts a force on a rock, the rock exerts an equal force back on your toe. The harder you hit your toe against it, the more force the rock exerts back on your toe (and the more your toe hurts).

34. Action: earth pulls on you Reaction: you pull on earth
Action and Reaction on Different Masses
Consider you and the earth
Action: earth pulls on you
Reaction: you pull on earth

35. Reaction: road pushes on tire Action: tire pushes on road

36. Reaction: gases push on rocket
Action: rocket pushes on gases

37. Consider hitting a baseball with a bat
Consider hitting a baseball with a bat. If we call the force applied to the ball by the bat the action force, identify the reaction force.
(a) the force applied to the bat by the hands
(b) the force applied to the bat by the ball
(c) the force the ball carries with it in flight
(d) the centrifugal force in the swing
(b) the force applied to the bat by the ball

38. 3rd Law of Motion Wrap Up
Video clip

39. Net Force How can you tell if something is equal and opposite?
Calculate it’s net force!

40. Fettuccine Lab
The height shall be at least 5 cm, supporting the book 5 cm above the table. All parts of the book should be at least 5 cm above the table.
Use all or part of the 20 pieces of fettuccine and all or part of the 1 m of masking tape. No additional tape or pasta may be used.
Tape must be used to secure the support structure. The structure must be one unit that can be picked up and moved
The structure must have a minimum of three points of support.
Test the pasta structure by placing a piece of paper on the structure first. Then a lightweight book is placed on the structure. The lightweight book is removed, and a medium weight book is placed on the structure. Last, a medium weight book is removed and a textbook is placed on the structure. To be successful, the structure must hold the item for ten seconds.

41. Tug of War
Today we will compete against the other science classes in a demonstration of Newton’s third law of motion.
All classes will do great, but Mrs. Crossman’s class WILL win 
Summarize your experience during Tug of War

42. Brief History of magnets
Magnets have been known for centuries.
The Chinese and Greeks knew about the “magical” properties of magnets.
They used the mineral “magnetite” to help in navigation, because it always pointed in the same direction.

43. Magnetic Forces Magnetic forces are produced by magnetic poles.
Ch 36 Magnetism Notes
Magnetic Forces
Magnetic forces are produced by magnetic poles.
Every magnet has both a North and South pole.
Like poles repel, unlike poles attract. *

44. Magnetic Fields Magnetic fields transmit magnetic forces.
Ch 36 Magnetism Notes
Magnetic Fields
Magnetic fields transmit magnetic forces.
Direction of the field is from N to S.
Field is stronger where field lines are closer.
Unit of magnetic field strength is the Tesla. The older unit Gauss is sometimes used.
Earth’s magnetic field strength is about 10-4 Tesla or about 1 Gauss *

45. Ch 36 Magnetism Notes
How Magnets Attract
A magnet near an unmagnetized piece of iron causes Attractive magnetic force on the iron
This causes the iron to become temporarily magnetized *

46. How big is the earths magnetic field?
Earth’s magnetic field extends far into space. We call this the “magnetosphere.”
When magnetic particles (mainly from the sun), called “solar wind”, strike the magnetosphere, we can see a phenomenon called the…
Aurora Borealis in the Northern Hemisphere.
Aurora Australis in the Southern Hemisphere.

47. How does a compass work?
We use the Earth’s magnetic field to find direction.
The needle of the compass always points toward the magnetic south pole.
YES! That is correct. We call this direction “North”. Remember!! Opposites Attract!

48. Electric Currents & Magnetism
Ch 36 Magnetism Notes
Electric Currents & Magnetism
Since moving charges create magnetic fields, an electric current creates a magnetic field.
A coil of wire can concentrate the magnetic field and create an electromagnet. *

49. Ch 36 Magnetism Notes
Motors
An electric motor uses a magnet to exert a force on a current-carrying coil of wire. *

50. Review Magnet and Iron Fillings Demonstration Truth About Magnets p.1
Answers

51. Review Newton’s First Law:
Objects in motion tend to stay in motion and objects at rest tend to stay at rest unless acted upon by an unbalanced force.
Newton’s Second Law:
Force equals mass times acceleration (F = ma).
Newton’s Third Law:
For every action there is an equal and opposite reaction.

52. 1stlaw: Homer is large and has much mass, therefore he has much inertia. Friction and gravity oppose his motion.
2nd law: Homer’s mass x 9.8 m/s/s equals his weight, which is a force.
3rd law: Homer pushes against the ground and it pushes back.

53. Bill Nye
Force and Motion Video

54. Jeopardy We will review for the test by playing a game of Jeopardy!
Force and Motion Jeopardy
Forces Jeopardy