2. Bell Ringer2-1-10  Tell me the 4 types of friction. (They were on the foldable!)  What is a force?  Give an example of a force.  Is gravity a force? Why or why not?

3. Videos Flight Attendant Fall Terminal Velocity Friction

4. Newton’s Laws of Motion Ch. 10 Section 3 I. Law of Inertia II. F=MA III. Action-Reaction

5. While most people know what Newton's laws say, many people do not know what they mean (or simply do not believe what they mean).

6. Newton’s Laws of Motion 1 st Law – An object at rest will stay at rest, and an object in motion will stay in motion at constant velocity, unless acted upon by an unbalanced force. 1 st Law – An object at rest will stay at rest, and an object in motion will stay in motion at constant velocity, unless acted upon by an unbalanced force. 2 nd Law – Force equals mass times acceleration. 2 nd Law – Force equals mass times acceleration. 3 rd Law – For every action there is an equal and opposite reaction. 3 rd Law – For every action there is an equal and opposite reaction.

7. 1 st Law of Motion (Law of Inertia) An object at rest will stay at rest, and an object in motion will stay in motion at constant velocity, unless acted upon by an unbalanced force. An object at rest will stay at rest, and an object in motion will stay in motion at constant velocity, unless acted upon by an unbalanced force.

8. 1 st Law Inertia is the tendency of an object to resist changes in its velocity: whether in motion or motionless. Inertia is the tendency of an object to resist changes in its velocity: whether in motion or motionless. These pumpkins will not move unless acted on by an unbalanced force.

9. 1 st Law The moon will keep revolving around the earth forever, unless acted on by an unbalanced force. The moon will keep revolving around the earth forever, unless acted on by an unbalanced force.

10. Moon in orbit around earth

11. 1 st Law Once airborne, unless acted on by an unbalanced force (gravity and air – fluid friction) it would never stop! Once airborne, unless acted on by an unbalanced force (gravity and air – fluid friction) it would never stop!

12. 1 st Law Unless acted upon by an unbalanced force, this golf ball would sit on the tee forever. Unless acted upon by an unbalanced force, this golf ball would sit on the tee forever.

13. Why then, do we observe every day objects in motion slowing down and becoming motionless without an outside force?  It’s a force we sometimes cannot see – friction.

14. Objects on earth, unlike the frictionless space the moon travels through, are under the influence of friction.

15. Friction When the unbalanced force is not obvious, friction is probably the cause of the change in the object’s motion.

16. There are four main types of friction: There are four main types of friction: Sliding friction: Sliding friction: ice skating Rolling friction: Rolling friction: bowling Fluid friction (air or liquid): Fluid friction (air or liquid): air or water resistance Static friction: Static friction: initial friction when moving an object What is this unbalanced force that acts on an object in motion?

17. Example Slide a book across a table and watch it slide to a rest position. The book comes to a rest because of the presence of a force - that force being the force of friction - which brings the book to a rest position.

18. In the absence of a force of friction, the book would continue in motion with the same speed and direction - forever! (Or at least to the end of the table top.) In the absence of a force of friction, the book would continue in motion with the same speed and direction - forever! (Or at least to the end of the table top.)

19. Newtons’s 1 st Law and You (Don’t let this be you. Wear seat belts.) Because of inertia, objects (including you) resist changes in their motion. When the car going 80 km/hour is stopped by the brick wall, your body keeps moving at 80 km/hour.

20. 2 nd Law Force equals mass times acceleration.

21. 2 nd Law The net force of an object is equal to the product of its mass and acceleration, or F= m x a.

22. 2 nd Law When mass is in kilograms and acceleration is in m/s 2, the unit of force is in newtons (N). When mass is in kilograms and acceleration is in m/s 2, the unit of force is in newtons (N). One newton is equal to the force required to accelerate one kilogram of mass at one m/s 2. One newton is equal to the force required to accelerate one kilogram of mass at one m/s 2.

23. 2 nd Law (F = M x A) How much force is needed to accelerate a 1400 Kilogram car 2 m/s 2 ? 1. Write the formula F = M x A 2. Fill in given numbers and units F = 1400Kg x 2 m/s 2 3. Solve for the unknown 2800 Kg- m/s 2 or 2800 N

24. Bell Ringer Work on Chapter 10 Vocabulary quickly. If you do not finish, you will need to finish for homework. If you have already finished, sit quietly and make sure your notebook is complete!

25. If mass remains constant, doubling the acceleration, doubles the force. If force remains constant, doubling the mass, halves the acceleration.

26. Newton’s 2 nd Law proves that different masses accelerate to the earth at the same rate, but with different forces. We know that objects with different masses accelerate to the ground at the same rate. However, because of the 2 nd Law we know that they don’t hit the ground with the same force. F = ma 98 N = 10 kg x 9.8 m/s2 F = ma 9.8 N = 1 kg x 9.8 m/s 2

28. Check Your Understanding  What is the force on a 1000 kg elevator that is falling freely at 9.8 m/s 2.?  What acceleration will result when a 12 N net force is applied to a 3 kg object?  A net force of 16 N causes a mass to accelerate at a rate of 5 m/s 2. Determine the mass.  How much force is needed to accelerate a 66 kg skier 1 m/s 2 ?

29. Check Your Understanding 1. What acceleration will result when a 12-N net force applied to a 3-kg object? 1. What acceleration will result when a 12-N net force applied to a 3-kg object? 12 N = 3 kg X 4 m/s 2 12 N = 3 kg X 4 m/s 2 2. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s2. Determine the mass. 2. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s2. Determine the mass. 16 N = 3.2 kg x 5 m/s 2 16 N = 3.2 kg x 5 m/s 2 3. How much force is needed to accelerate a 66-kg skier 1 m/sec/sec? 3. How much force is needed to accelerate a 66-kg skier 1 m/sec/sec? 66 kg-m/s 2 or 66 N 4. What is the force on a 1000-kg elevator that is falling freely at 9.8 m/sec/sec.? 4. What is the force on a 1000-kg elevator that is falling freely at 9.8 m/sec/sec.? 9800 kg-m/s 2 or 9800 N 9800 kg-m/s 2 or 9800 N

32. Vocabulary p. 366 Vocabulary p. 366 Sections 1-4 (20 words) Sections 1-4 (20 words)

33. Chapter 10 Section 4 Notes

34. Newton’s 3 rd Law of Motion/ Action-Reaction Law For every action, there is an equal and opposite reaction. For every action, there is an equal and opposite reaction.

35. 3 rd Law According to Newton, whenever objects A and B interact with each other, they exert forces upon each other. When you sit in your chair, your body exerts a downward force on the chair and the chair exerts an upward force on your body.

36. 3 rd Law There are two forces resulting from this interaction - a force on the chair and a force on your body. These two forces are called action and reaction forces.

37. Newton’s 3rd Law in Nature Think about a fish swimming in water. Think about a fish swimming in water. A fish uses its fins to push water backwards. In turn, the water reacts by pushing the fish forwards, propelling the fish through the water. A fish uses its fins to push water backwards. In turn, the water reacts by pushing the fish forwards, propelling the fish through the water. The size of the force on the water equals the size of the force on the fish. The size of the force on the water equals the size of the force on the fish. The direction of the force on the water (backwards) is opposite the direction of the force on the fish (forwards). The direction of the force on the water (backwards) is opposite the direction of the force on the fish (forwards).

38. 3 rd Law Flying gracefully through the air, birds depend on Newton’s third law of motion. As the birds push down on the air with their wings, the air pushes their wings up and gives them lift.

39. Consider the flying motion of birds. A bird flies by use of its wings. The wings of a bird push air downwards. In turn, the air reacts by pushing the bird upwards. Consider the flying motion of birds. A bird flies by use of its wings. The wings of a bird push air downwards. In turn, the air reacts by pushing the bird upwards. The size of the force on the air equals the size of the force on the bird; the direction of the force on the air (downwards) is opposite the direction of the force on the bird (upwards). The size of the force on the air equals the size of the force on the bird; the direction of the force on the air (downwards) is opposite the direction of the force on the bird (upwards). Action-reaction force pairs make it possible for birds to fly. Action-reaction force pairs make it possible for birds to fly.

41. Other examples of Newton’s Third Law The baseball forces the bat to the left (an action). The baseball forces the bat to the left (an action). The bat forces the ball to the right (the reaction). The bat forces the ball to the right (the reaction).

42. 3 rd Law Consider the motion of a car on the way to school. A car is equipped with wheels which spin forward. As the wheels spin, they grip the road and push the road backwards. Consider the motion of a car on the way to school. A car is equipped with wheels which spin forward. As the wheels spin, they grip the road and push the road backwards.

44. 3 rd Law The reaction of a rocket is an application of the third law of motion. Various fuels are burned in the engine, producing hot gases. The hot gases push against the inside tube of the rocket and escape out the bottom of the tube. As the gases move downward, the rocket moves in the opposite direction.

45. Momentum Momentum = mass x veloctiy The SI unit for momentum is kg x m/s and the direction. Ex. 58 kg bike traveling east at 12 m/s. What is the momentum? Answer: 696 kg x m/s east Momentum increases if the mass or velocity of the object increases.

46. 1. Who was the scientist who gave us the Laws of Motion? 2. How many Laws of Motion are there? 3. What is another name for the third law of motion? 4. Which law explains why we need to wear seatbelts? 5. Which law says that force is equal to mass times acceleration (F = M x A)? 6. Which law says that heavier objects require more force than lighter objects to move or accelerate them? 7. Which law explains how rockets are launched into space? 8. Which law says that for every action there is an equal and opposite reaction?

47. 1. 1. Sir Isaac Newton 2. 2. three 3. 3. Action-Reaction Law 4. 4. First Law of Motion 5. 5. Second Law of Motion 6. 6. Second Law of Motion 7. 7. Third Law of Motion 8. 8. Third Law of Motion

48. Exit Quiz # 4 Fill in the blanks for questions 1 and 3.   Newton’s 1 st Law: An object at rest must stay at rest, and an object in motion must stay in motion, at constant velocity, unless acted on by an unbalanced ______.   If a 0.5 kg leaf falls from a tree at an acceleration of 1 m/s 2, what is the force with which it hits the ground? (Remember F = m x a.)   Newton’s 3 rd Law: For every action there is an equal and _______ reaction.   What unit measures force?