1. Newton’s Laws of Motion

2. What happens when one particle collides with another particle (of the same mass)? What is an elastic collision? What is an inelastic collision? How would the situation change if one particle was more massive than the other particle? http://www.picgifs.com/grap hics/c/collision/graphics- collision-644627.gif

3. How is the speed of an object defined? How does relative speed change the outcome of a collision? What is the momentum of an object/particle?

4. Compare the momentum of two objects of different masses moving with the same speed. Which has a greater momentum? Explain. What is a force? How does a force affect the motion of a object/particle?

5. Can one particle exert a force on another particle without itself being affected? How does the force exerted on one particle compare with the force on the other particle during the collision?

6. A collision (interaction) between two objects of different masses occurs – say a bee and a windshield of a car. How do the forces on each object compare at impact? How do the objects’ resulting accelerations compare at impact?

7. Collisions between objects come somewhere in between two extremes: elastic and inelastic. An elastic collision is one in which the two objects bounce off one another. An inelastic collision is one in which the two objects stick together.

8. Inertia is the resistance to change in motion (AKA – the acceleration) of an object. The inertia (AKA – the mass) of an object is measured in kilograms (sometimes in grams).

9. Speed is the time rate at which distance is covered. Example 1: If a car has a speed of 70 miles/hour, what does this mean? How much time elapses every 70 miles? How many miles are traveled every hour?

10. The speed of an object can be determined by dividing the distance by the time interval it took to cover that distance. In symbols: S = d/t Example 2: if a marble travels a distance of 30 centimeters in about 2 seconds, then what is its speed? S = d/t = 30 cm/2 s = 15 cm/s

12. Observations with colliding speeds: Marble 1 (inertia: ________g Marble 1 (inertia: _______g Marble 1 (inertia: _______g Marble 1 (inertia: _______g 1 (medium speed) 2 (faster speed) 3 (½medium speed)

13. Follow the general directions on the lab sheet and commence learning! At the completion of investigation 1 discuss your data and observations within your group, write a summary of your observations, and finally debrief with your instructor (as a group or class).

14. What happens when a particle collides with another particle of similar mass? In general, if the objects do not stick together (an elastic collision), the initially moving object will come to rest (stop moving) and the initially stationary object will move with about the same speed as the once moving object.

15. How does increasing (or decreasing) the speed of the starting marble affect the speeds of both marbles after the collision? In general, during an elastic collision between two objects of the same mass, whatever speed the first object has will be transferred to the second object.

16. What happens during the collision between the moving marble and the stationary marble? Or what causes the stationary marble to begin moving, and the moving marble to come to rest? During this interaction something called a force causes both of these effects to occur.

17. A force is a push or a pull on an object. During the collision, was the force on the stationary object a push or a pull? Explain. A push. During the collision, which way was the force on the stationary marble acting? In the direction that it began moving.

18. During the collision, which way was the force on the initially moving marble acting and was it a push or a pull? It was a push in the opposite direction of its initial motion. The force made it stop, or nearly stop.

19. Compare the size of the forces acting on each marble during the collision. Is one larger than the other? Explain. They are equal in size.

20. How would you describe the total motion of the two-marble system with similar masses before and after the collision? The total quantity of motion before and after a collision between objects of the same mass is the same. Whenever a quantity stays the same it is said to be conserved.

21. http://www.youtube.com/watch?v=by-7kkAu2Pg

22. 1642 - 1727

23. The velocity of a body remains constant unless the body is acted upon by an external force. Meaning - If something is moving, it is going to continue to move unaffected until some force or other object is encountered.

24. Net Force = 0 (upward force on the book cancels downward force on the book; also known as balanced forces)

25. Net Force = 0 (forces balance or cancel each other out)

26. Net Force  0 (forces do not cancel each other out) Say a book is slid across the table to a friend…what happens?

27. The amount of inertia of an object is measured by its mass. The units for mass in the metric system is grams. The standard for mass in the metric system is the kilogram (1000 grams).

28. If inertia is the resistance to a change in motion, then what will happen if the stationary marble is replaced with one of a greater mass? How will the resulting speeds of each marble compare after the collision? How will differing speeds of the smaller marble affect the results?

29. Follow the directions on the lab sheet for Part II, and commence learning! At the completion of investigation Part II discuss your data and observations within your group, write a summary of your observations, and finally debrief with your instructor (as a group or class).

32. What happens when a particle of smaller mass collides with another particle of larger mass? In general, during an elastic collision with an initially moving smaller mass colliding with a stationary larger mass, the result is that the larger mass will move in the same direction as the smaller mass before the collision, but with a smaller speed; and the smaller mass will move in the opposite direction with a smaller speed.

33. Using the relative inertia of each marble, describe how the inertia of an object affects its motion. During an interaction (collision), the object with less inertia has a greater change of motion than the object with more inertia.

34. How did increasing or decreasing the speed of the less massive marble affect the resulting motion of each marble? The more massive marble had a greater change in motion; it moved with a greater speed. The less massive marble had a greater change in motion as well in the opposite direction.

35. In Part I, speed or motion was “conserved.” Was speed “conserved” in Part II? Explain. No. Before the interaction (collision) only the smaller marble had a speed in one direction. After the interaction, the smaller marble had a speed in the opposite direction, and the larger marble had a small speed in the same direction as the smaller before the collision.

37. Compare the size of the forces acting on each marble during the collision. Is one larger than the other? Before you answer, remember that each marble has a different amount of mass (inertia). Explain. They are equal in size. The smaller mass marble has less of a resistance to changing its motion so we see a larger change in its motion, and likewise the stationary more massive marble has a smaller change in its motion. Therefore even though the forces (the causes) are the same size on each marble, the resulting changes in motion (effects) are different.

38. Using what you learned from Parts I & II predict what will happen in Part III. What will happen when a larger mass marble collides with a stationary smaller mass marble? Which marble will have a larger change in motion?

39. Follow the directions on the lab sheet for Part III. At the completion of investigation Part III discuss your data and observations within your group, write a summary of your observations, and finally debrief with your instructor (as a group or class).

41. What happened when a larger mass marble collided with a stationary smaller mass marble? The larger mass’s speed got smaller, and the smaller mass speed increased. Which marble had a larger change in motion? The smaller mass marble.

42. 1 st Law (the law of inertia): an object will remain in motion at a constant speed in a straight line, or at rest, until acted upon by a net force. A net force on an object causes the object to accelerate (change its motion). A net force is the sum of all the forces acting on an object.

43. Two possibilities (flow chart – The Physics Classroom.com)

44. Net Force = 0 (forces balance or cancel each other out)

45. Net Force  0 (forces do not cancel each other out) Say a book is slid across the table to a friend…what happens?

46. The amount of inertia of an object is measured by its mass. The units for mass in the metric system is grams. The standard for mass in the metric system is the kilogram (1000 grams).

47. The Mechanical Universe : The Law of Inertia Practice with the law of inertia.

48. If an object accelerates (changes its motion) then a agent called a net force acts on it. A force is a push or a pull. There are two categories of forces – contact and non-contact forces.

49. What might be an example of a contact force? Lifting a book with your hand, friction between your shoe and the ground, pulling a door handle What might be an example of a non-contact force? Dropping a pencil on the floor (the earth’s gravitational attraction to it). Your hair attracted to a plastic comb (a static electric force of attraction). A magnet picking up a paper clip (a magnetic force of attraction).

50. Newton’s 2 nd Law of Motion: the acceleration (change of motion) on an object is directly proportional to the net force acting on it. As the net force increases, the acceleration increases; as the net force decreases, the acceleration decreases.

51. Newton’s 2 nd Law - continued If the mass (inertia) changes, then the resulting acceleration changes inversely. For a given constant forces if the mass increases, the acceleration decreases; if the mass decreases the acceleration increases.

52. Newton’s 2 nd Law - continued These relationships are summarized in the equation: Force = mass x acceleration, or symbolically F = ma

53. Newton’s 2 nd Law of Motion – Example Suppose a 800 kg car has an acceleration of 8 m/s/s (it’s speed increases 8m/s every second). What is the net force on the car?

54. Suppose a 800 kg car has an acceleration of 8 m/s/s. What is the net force on the car? From the 2 nd law: F = ma = (800kg)(8 m/s/s) = 6400 N

55. Newton’s 2 nd Law Example 2 Suppose a 1000 kg car smashes into a telephone pole that exerts a force of 200,000 N on the car before breaking. What is the acceleration of the car?

56. Suppose a 1000 kg car smashes into a telephone pole that exerts a force of 200,000 N on the car before breaking. What is the acceleration of the car? Again F = ma  -200,000 N = (1000kg)(a) (note the negative sign indicates the direction of the force) 200,000N/1000kg = -200 m/s/s

57. Newton’s 3 rd Law: forces always occur in pairs, equal in size and opposite in direction.

58. In the example below: the ball exerts a force on the catcher glove. What is the reaction force? Symbolically: F glove by ball Answer: The force on the ball by the glove. Symbolically: F ball by glove

59. What is the reaction force to F pin by ball ? Answer: The force on the ball by the pin. Symbolically: F ball by pin Are you seeing the pattern?

60. Newtons 3 rd law Mythbusters http://www.youtube.com/watch?v=yneECzfVkYk