1. NOTE: This presentation was not made for public use. Please do not use this presentation without my permission and the permission of each of the authors of the photographs, quotes, and other materials that they contain. Thank you, Vicki Hughes Labs and Activities that go with this presentation: Newtonian Demonstrator Trains

2. Newton’s Laws of Motion and Gravitation Force is a push or a pull. A Push Or A Pull Net Force = sum of al the forces acting on an object. 2 + (-2) = 0 2-2 2 + 2 = 4 22

3. Balanced & Unbalanced Forces Balanced force – opposite and equal forces acting on the same object that result in NO motion of the object Unbalanced forces – two or more forces of unequal strength or direction acting upon an object results in the motion of the object

4. Forces in Opposite Directions Net Force is equal to the difference between the two forces acting on an object. Why does the block stop falling? The table pushes up on the block with a force of 20 Newtons. Newton = the unit of measure for force 1 Newton = kg x m/s 2 Why does the block fall downward? Gravity pushes down on the block with a force of 20 Newtons. Net Force = 20 – 20 = 0 Newtons

5. Forces in the Same Direction Net Force is equal to the sum between the two forces acting on an object. 40 Newtons 20 Newtons+ 60 Newtons

6. Forces in Opposite Directions 40 Newtons 20 Newtons-

7. Newton’s 1st Law of Motion Also called “The Law of Inertia” –an object at rest will remain at rest and an object in motion will remain in motion… Unless acted upon by another force http://www.youtube.com/watch?v=NYVMlmL0BPQ&feature=related

8. Newton’s 1st Law of Motion (cont.) –an object at rest will remain at rest –an object in motion will remain in motion at a constant velocity until acted on by another force. Remember: The greater the mass of an object the greater the inertia. Inertia Inertia = tendency of an object to resist changes in its motion. Physics of Car Crashes http://www.youtube.com/watch?v=yUpiV2I_IRI http://www.youtube.com/watch?v=yUpiV2I_IRI

9. Force = mass x acceleration F=ma (a= F/m and m= F/a) What is the common unit for mass? What is the basic unit for acceleration? Therefore the basic unit for Force is (kilogram)( meter/sec 2 ) An object with a mass of 1 kg accelerating at 1 m/s/s has a force of 1 Newton Kilogram Meter/sec 2 Newton’s 2nd Law of Motion

10. Newton’s 2 nd Law & Gravitation Everyone has heard of the FORCE of gravity Gravity: the force that pulls objects towards each other Since gravity is a force it also obeys Newton’s second law (F=ma) Objects fall at the same speed. Their acceleration is the same. All objects accelerate at the same rate. Here on Earth the rate is: A g = 9.8 m/s 2 Air resistance keeps things from falling equally gravity

11. Weight is the force of gravity acting on an object’s mass. The formula for weight: Weight = mass x gravity Newton’s 2 nd Law & Weight

12. Your weight on other planets & 3 different types of stars http://www.exploratorium.edu/ronh/weight/

13. – For every action there is an equal & opposite reaction. Newton’s 3rd Law of Motion

14. Newton’s 3 rd Law of Motion (cont.) : – For every action there is an equal & opposite reaction. A swinging ball will swing equally in both directions. However, in this Newtonian Demonstrator, as one ball hits the group, the energy is transferred through the group to the end ball on the opposite side. The end ball reacts with an equal amount of energy. http://www.youtube.com/watch?v=JadO3RuOJGU http://www.youtube.com/watch?v=yVkdfJ9PkRQ

15. Rolling friction Fluid friction Sliding friction Friction – opposition to motion. ACT 21 (only #1 & 2)

16. Momentum An object’s momentum is directly related to both its mass and velocity. – Momentum = mass x velocity For some reason, maybe because mass is designated as “m” in formulas, momentum is designated as “ p ”. Therefore: p = mv Momentum = mass x velocity

17. Momentum (cont.) The unit for mass is kg, the unit for velocity is meter/second, therefore the unit for momentum is kg m/sec Conservation of Momentum: – When two or more objects interact (collide) the total momentum before the collision is equal to the total momentum after the collision

18. Momentum – 2 moving objects During this collision the speed of both box cars changes. The total momentum remains constant before & after the collision. The masses of both cars is the same so the velocity of the red car is transferred to the blue car. Faster Slower Faster Train Cars Demo

19. Momentum – 2 moving objects During this collision the speed of both box cars changes. The total momentum remains constant before & after the collision. The masses of both cars is the same so the velocity of the red car is transferred to the blue car. 10 m/s 5 m/s 10 m/s

20. Momentum – 1 moving object During this collision the speed of the red car is transferred to the blue car. The total momentum remains constant before & after the collision. The masses of both cars is the same so the velocity of the red car is transferred to the blue car. Moving Stopped Moving

21. Momentum – 2 moving objects During this collision the speed red car is transferred to the blue car. The total momentum remains constant before & after the collision. The masses of both cars is the same so the velocity of the red car is transferred to the blue car. 10 m/s 0 m/s (Stopped) 0 m/s 10 m/s

22. Momentum – 2 connected objects After this collision, the coupled cars make one object w/ a total mass of 60,000 kg. Since the momentum after the collision must equal the momentum before, the velocity must change. In this case the velocity is reduced from 10 m/sec. to 5 m/sec. Hooked together here Moving Stopped Moving

23. Momentum – 2 connected objects After this collision, the coupled cars make one object w/ a total mass of 60,000 kg. Since the momentum after the collision must equal the momentum before, the velocity must change. In this case the velocity is reduced from 10 m/sec. to 5 m/sec. 10 m/s 0 m/s (Stopped) 5 m/s

24. Any Questions? ACT 22 (omit #3)