2. Force Unit FORCE

3. Force Unit Unbalanced Forces

4. Forces – Day 1 Objectives I will knowthe nature of forces and their interactions with matter. I will be able todescribe and solve for balanced and unbalanced forces.

5. How do forces affect the motion of an object? A force can cause a resting object to move, or it can accelerate a moving object by changing the object’s speed or direction. Can you give some examples of when you could apply a force? What Is a Force? A force is a push or a pull that acts on an object.

6. One newton(N) is the force that causes a 1-kilogram mass to accelerate at a rate of 1 meter per second each second (1 m/s 2 ). 1 N =1 kgm/s 2 What is the unit for force?

7. When the forces on an object are balanced, the net force is zero, and there is no change in the object’s motion. Combining Forces When an unbalanced force acts on an object, the object accelerates. How do forces affect the motion of an object?

8. The net force is the overall force acting on an object after all the forces are combined. NET Forces Forces in the same direction add together. Can you think of an example of two forces in the same direction, that would make a bigger force?

9. Let’s do a little activity! 1. Everyone take your physical science book and stand up. 2. Let’s pretend you will gently push the book forward along the floor with a force of 10 N. 3. Stop. 4. Now push the book along the floor a little harder with another forward force of 20 N. 5. Return to your seat. 6. What was your net force? 10 N + 20 N = 30 N My NET FORCE WAS 30 N!

10. What would happen if forces would occur in opposite directions? Forces in the opposite direction subtract from one another.

11. Let’s do another little activity! 1. Everyone take your physical science book and stand up. 2. Let’s pretend you will gently push the book along the floor forward with a force of 20 N. 3. Stop. 4. Now push the book along the floor in the opposite direction with a little harder with a force of 30 N. 5. Return to your seat. 6. What was your net force? 20 N - 30 N = -10 N My NET FORCE WAS -10 N!

12. The two groups pull with equal forces in opposite directions. The forces combine to make a net force of zero. An example of combining forces:

13. Forces can add together or subtract from one another. Combining Forces Adding forcesSubtracting forces

14. Forces can add together or subtract from one another. Combining Forces Adding forcesSubtracting forces Equal and opposite forces

15. Small Group Practice What is the net force of the following: 1.60 N east, 80 N west 2.45 N north, 20 N north 3.25 N to the right, 55 N to the left 4.90 N south, 90 N north 5.35 N south, 15 N north 6.5 N to the left, 9 N to the left 7.3 N to the left, 3 N to the right Next to your answer, write if it is balanced or unbalanced.

16. Group Practice -- answers What is the net force of the following: 1.60 N east, 80 N west = 20 N west; unbalanced 2.45 N north, 20 N north = 65 N north; unbalanced 3.25 N to the right, 55 N to the left = 30 N left; unbalanced 4.90 N south, 90 N north = 0 N; balanced 5.35 N south, 15 N north = 20 N south; unbalanced 6.5 N to the left, 9 N to the left = 14 N left; unbalanced 7.3 N to the left, 3 N to the right = 0 N; balanced Next to your answer, write if it is balanced or unbalanced.

17. In what direction does Earth’s gravity act? Gravity Earth’s gravity acts downward toward the center of Earth.

18. How do gravity and air resistance affect a falling object? Gravity causes objects to accelerate downward, whereas air resistance acts in the direction opposite to the motion.

19. This flying squirrel takes advantage of air resistance to slow its fall and increase the distance covered in the jump. Example:

20. Summary “Think, Pair & Share” Can you think of other examples of forces? Baseball hitting a ball Foot kicking a soccer ball Car hitting another car in an accident Fingers pushing a key on a keyboard

21. Summary Day 1 Using complete sentences, explain the forces involved with this picture. Also, how would you describe the net force?

22. Summary Day 1 -- answer Earth exerts an attractive, downward force on this boulder. The supporting rock exerts an upward force on the boulder. The forces are balanced.

23. End of What is Force Notes page

24. Put this on back of what is force pages Newton’s Law of Universal Gravitation: Every mass attracts every other mass with a force directly proportional to the masses and inversely proportional to the distance between them.

25. Does the sun’s force have more effect on Earth or the dwarf planet Pluto? Earth (closer)

26. Force Unit Newton’s 1 st & 3 rd Laws of Motion

27. Objectives Take notes Cornell Style in your Notebooks over this section I will understand Newton’s first and third Laws of Motion. I will be able to describe examples of Newton’s first and third Laws of Motion. I will be able to review the Inverse Square Law.

28. Newton’s 1 st Law of Motion

29. 1 st Law: An object in motion will stay in motion,

30. an object at rest will stay at rest,

31. unless acted on by an outside force. What outside force is slowing the ball to a stop? FRICTION

32. VOCABULARY: Inertia: the tendency of an object to resist any change in its motion.

33. Mass is a quantitative measure of inertia.

34. Which boxer has more inertia?

35. The bigger one! WHY? MORE MASS!

36. Turn to a partner – Which dog has more inertia?

37. THE BIGGER ONE! more mass – more inertia!

38. Newton’s Third Law of Motion

39. 3 rd Law: For every action – there is an equal but opposite reaction!

40. One force is called the ACTION FORCE. The other force is called the REACTION FORCE. a. It does not matter which is called action or reaction. b. They are a pair in a single interaction.

41. c. They are EQUAL in strength d. They are opposite in direction. Can you give examples of Newton’s 3 rd Law?

42. rocket fuel Examples:

43. If you have TWO DIFFERENT masses. a. They will have equal forces. b. Their velocities will be different.

44. Cannonball’s velocity is greater Example of different velocities Cannon’s velocity is smaller

45. This is due to the 2 nd Law A small mass = a greater acceleration A larger mass = a smaller acceleration

46. Push down on your lab table. Turn to a partner

47. Discuss what each of you think the lab table does to your hand. Table pushes back!

48. They are EQUAL but OPPOSITE reactions! Table pushes back!

49. If you have unequal Forces then you have acceleration – NOT the 3 rd Law.

50. Bottom of Cornell Notes Using complete sentences describe two examples of the 1 st law that you see occur in your life and describe two examples of the 3 rd law that you see occur in your life.