Chapter: Newton’s Laws of Motion

2. Table of Contents Chapter: Newton’s Laws of Motion Section 1: Motion Section 2: Newton’s First Law Section 3: Newton’s Second Law Section 4: Newton’s Third Law

3. Motion 1 A. Motion- a change in position 1. Distance- the entire path an object travels.

4. Motion 2 2. Displacementis the distance and direction between starting and ending positions.

5. Motion 3 3. Relative motion- an object’s position change is described in terms of a reference point.

6. Motion 4 B. Speed- distancetraveled divided by the time needed to travel the distance, or speed= distance/time

7. Motion 5 S=d/t t=d/s d=s x t 1. Constant speed- speed is the same at any given moment in time.

8. Motion 6 2. Speed at a particular instant in time is instantaneous speed.

9. Motion 7 C. Velocity- displacement divided by time, or v= displacement/time. 1. Formula calculates average velocity.

10. 2. Includes concept of direction as well as speed. 8

11. Motion 9 D. Change in velocity divided by the time required for the change to occur is acceleration.

12. 1. Acceleration occurs when an object slows down as well as speeds up. 10

13. 2. For an object traveling in a straight line, a change in speed can be used to calculate acceleration. 11

14. Motion 12 Calculating Acceleration a. acceleration= (final speed-initial speed)/time

15. b. Initial speed is zero for objects at rest. 15

16. Motion 16 3. Turning or changing direction is also acceleration.

17. Section Check 1 Question 1 Which is the distance and direction between starting and ending positions? A. acceleration B. displacement C. speed D. velocity

18. Section Check 1 Answer The answer is B. Displacement can be zero if you travel in a path that leads you back to where you started.

19. Section Check 1 Question 2 Explain what is meant by relative motion. Answer The position of an object is described relative to another object. Taking some other object as a reference point, we can say whether or not a given object is in motion.

20. Section Check 1 Question 3 What is calculated by figuring the displacement over time? A. acceleration B. average speed C. speed D. velocity

21. Section Check 1 Answer The correct answer is D. The formula for velocity is v = d/t.

22. A. Laws of motion are sets of rules first stated by Isaac Newton. Newton’s First Law 2

23. 1.Force- a push or pull with size and direction. 2. Contact force involves objects touching each other. Newton’s First Law 2

24. 3. Long-range forces include gravity,magnetism, and electricity.4. When scientists measure force, they use the newton, abbreviated N. Newton’s First Law 2

25. B. First Law of motion- an object will remain at rest or move in a straight line with constant speed unless a force acts on it. Newton’s First Law 2

26. 1. Inertia measures an object’s tendency to remain at rest or keep moving. Newton’s First Law 2

27. 2. Inertia is related to mass; objects with more mass have more inertia. Newton’s First Law 2

28. C. Adding forces- sometimes more than one force acts on an object. Newton’s First Law 2

29. 1. Balanced forces- forces that are equal but in opposite directions, canceling each other. Newton’s First Law 2

30. 2. If one force is greater than another, a change in motion will result from unbalanced forces. Newton’s First Law 2

31. 3. An object acted on by an unbalanced force changes velocity. Newton’s First Law 2

32. Section Check 2 Question 1 A force is a _______ or a _______. Answer Force is a push or a pull.

33. Section Check 2 Question 2 A force exerted between two objects that are not touching is known as _______. Answer The answer is a long-range force. Gravity is a long-range force; although we are not touching the Sun, our planet is being acted on by the Sun to keep it in orbit.

34. Section Check 2 Question 3 You try to push a desk across the floor one direction but a friend is trying to push it the opposite direction. As a result, the desk doesn’t move. This is an example of what kind of forces? A. balanced forces B. continuing forces C. extended forces D. unbalanced forces

35. Section Check 2 Answer The answer is A. When forces are balanced, the net force is zero.

36. A. Second law of motion- an object acted on by an unbalanced force will accelerate in the direction of the force. Newton’s Second Law 3

37. 1. Newton’s Second Law 3

38. 2. Force is equal to the combination of all forces, or the total force that acts on an object. Newton’s Second Law 3

39. B. Second law can also be used to find force if mass and acceleration are known. Newton’s Second Law 3

40. 1. Near Earth’s surface, the force of gravity causes all objects to fall with the same acceleration-9.8 m/s2. Newton’s Second Law 3

41. a. For any object that is falling, the force of gravity equals mass times acceleration due to gravity, or F=m x (9.8m/s2) Newton’s Second Law 3

42. b. Because weight is the force of gravity on an object, an object’s weight equals mass times acceleration due to gravity, or weight=m x (9.8 m/s2) Newton’s Second Law 3

43. 2. Weight and mass are not the same thing. Newton’s Second Law 3

44. a. Weight changes when the acceleration due to gravity changes.b. Mass remains the same no matter what weight is. Newton’s Second Law 3

45. C. Friction- a force that resists motion and is always present between two moving forces. Newton’s Second Law 3

46. 1. Static friction- keeps a stationary object from moving on a surface when a force is applied to the object. Newton’s Second Law 3

47. 2. Sliding friction- occurs when two surfaces slide past each other; slows down the moving object. Newton’s Second Law 3

48. 3. Rolling friction- friction between a surface and a wheel when the wheel rolls over the surface. Newton’s Second Law 3

49. 4. Air resistance- typical action of air molecules on a forward-moving object, slowing its motion. Newton’s Second Law 3

50. Section Check 3 Question 1 Explain Newton’s second law of motion. Answer Newton’s second law says that the acceleration of an object is equal to the net force on it divided by its mass.