Forces

Powerpoint on forces and friction/gravity
5th grade

1. What are Forces? October 20, 2014

2. What forces do you think are acting on you right now while you’re sitting in your seat?

3. There are forces acting on you all the time whether you know it or not! Gravity is pulling you down The ground is pushing you up Air is squeezing you from every direction Your body is pushing back at the air

4. When forces are balanced, they cancel out and you don ’ t notice them. But when forces don ’ t balance, things happen… THINK! What would happen if we took the force of gravity away?

5. A force is a PUSH or a PULL Forces can cause an object to move, change speed, change direction, change shape, or stop Forces have size and direction

6. When you drop your pencil, gravity is pulling it to the ground When you are walking around, your feet are pushing down onto the ground

7. Force Facts Measured in Newtons (N) Always act in pairs Cannot be seen, but the effect can be seen Measured using a spring scale

8. Measuring Force How many Newtons will it take for me to drag your science binder across the desk?

9. Net Force Net force : the size of all the forces acting on an object If two forces acting on an object are in the SAME direction, you ADD the forces together If two forces acting on an object are in the OPPOSITE direction, you SUBTRACT the forces

10. Written with a magnitude and direction Ex: Force Net = 30 N 

11. Net force = 50 N  7 5 N  If two forces acting on an object are in the SAME direction, you ADD the forces together

12. Net force = 500 N 100 N If two forces acting on an object are in the OPPOSITE direction, you SUBTRACT the forces

13. B alanced Forces Forces that cancel each other out Net force = ZERO There is no change in motion

14. Balancing your science textbook on your desk Force net =

15. Net force =

16. Unbalanced Forces When forces acting on an object do not cancel out Net force does not = zero Produce a change in motion

17. Net force =

18. Checkpoint What is the unit used for measuring a force? Newtons 2. What tool is used to measure forces? Spring Scale

19. 3. Find the net force 950 N  625 N 

20. Review Find the net force 600 N   60 N

21. 2. Find the net force 525 N  50 N 

22. Forces that act against motion… If you kick a soccer ball on grass, what will start to slow it down?

23. The enemy of motion Friction : force that occurs when 2 objects rub against each other Always acts in the direction opposite to the direction of motion Will slow the motion of an object or stop it Creates heat

24. Every object causes friction, some more than others It may look smooth, but it is covered in tiny bumps and dents

25. Friction can be beneficial E veryday life would be a lot different without it THINK! What would happen if the floor in the classroom was ice instead of carpet?

26. When would decreasing friction be beneficial?

27. Is it possible to pick up a bottle full of rice with just a pencil? YES!

28. 4 Types of Friction Static friction Sliding friction Rolling friction Fluid friction

29. Fluid Friction- Air Resistance Caused by friction of the air against an object Objects with more surface area experience greater air resistance and move more slowly

30. Gravity Force that pulls objects towards each other Law of gravitational force : The force of gravity depends on the distance between the objects and their masses

31. Which objects have the greatest force of gravity? A B C D A and C D and B B and C A and D

32. Mass : the amount of matter in an object (g ) Weight : measure of the force of gravity on an object ( N)

33. All objects fall at the same rate towards the earth because gravity pulls on every object the same amount Air resistance slows objects down What would hit the ground first, a pencil or a ball? What about a sheet of paper and a balled up sheet?

34. An object’s weight can change if you went from the earth to the moon, but your mass would stay the same. Ex: G ravity on moon is 1.622 m/s 2

35. THINK! What would happen if we drop a feather and a hammer on earth? What if we were on the moon? Hammer-feather drop What is happening?

36. Zero G Experience http:// www.gozerog.com

37. Checkpoint Is your mass the same on earth and the moon? Is your weight the same on the earth and moon? What forces will effect a soccer ball that has been kicked?

38. StudyJams Video