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Table of Contents

Table of Contents. Chapter Preview 10.1 The Nature of Force 10.2 Friction, Gravity, and Elastic Forces 10.3 Newton’s First and Second Laws 10.4 Newton’s Third Law 10.5 Rockets and Satellites. Chapter Preview Questions. 1. How do you know an object is in motion? a. It has inertia.

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Table of Contents

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  1. Table of Contents Chapter Preview 10.1 The Nature of Force 10.2 Friction, Gravity, and Elastic Forces 10.3 Newton’s First and Second Laws 10.4 Newton’s Third Law 10.5 Rockets and Satellites

  2. Chapter Preview Questions • 1. How do you know an object is in motion? • a. It has inertia. • b. It has mass. • c. It is changing position. • d. It has a reference point.

  3. Chapter Preview Questions • 1. How do you know an object is in motion? • a. It has inertia. • b. It has mass. • c. It is changing position. • d. It has a reference point.

  4. Chapter Preview Questions • 2. What is velocity? • a. speed • b. speed in a given direction • c. miles per hour • d. change in speed over time

  5. Chapter Preview Questions • 2. What is velocity? • a. speed • b. speed in a given direction • c. miles per hour • d. change in speed over time

  6. Chapter Preview Questions • 3. Which is the best definition of acceleration? • a. change in velocity • b. change in reference point • c. increase in speed • d. decrease in speed

  7. Chapter Preview Questions • 3. Which is the best definition of acceleration? • a. change in velocity • b. change in reference point • c. increase in speed • d. decrease in speed

  8. Chapter Preview Questions • 4. If an object starts out at rest and accelerates to 100 m/s, what is its initial speed? • a. -100 m/s • b. 0 m/s • c. 100 m/s • d. 32 m/s

  9. Chapter Preview Questions • 4. If an object starts out at rest and accelerates to 100 m/s, what is its initial speed? • a. -100 m/s • b. 0 m/s • c. 100 m/s • d. 32 m/s

  10. You drop a tennis ball and a baseball at the same time. Why do the balls fall to the floor? What causes an object’s velocity to change?

  11. Latin Word Origins Center Centripetal force

  12. Latin Word Origins Together, with Compression

  13. Latin Word Origins Throw Projectile

  14. Latin Word Origins Press Compression

  15. Latin Word Origins Forward, before Projectile

  16. Latin Word Origins Stretch Tension

  17. Apply It! Look at pro- and jacere and predict the meaning of projectile. Revise your definition as needed as you read the chapter. Look for words with these Latin origins as you read the chapter. Sample: I see that pro- means “forward” and that jacere means “to throw.” By combining the two I get the definition of projectile.

  18. End of Chapter Preview

  19. Section 1:The Nature of Force • How is a force described? • How do balanced and unbalanced forces affect an object’s velocity?

  20. Combining Force Vectors • The strength and direction of the individual forces determine the net force.

  21. Unbalanced Forces • Unbalanced forces acting on an object result in a net force and cause a change in the object’s velocity.

  22. Balanced Forces • Balanced forces acting on an object do not change the object’s velocity.

  23. Links on Force • Click the SciLinks button for links on force.

  24. End of Section:The Nature of Force

  25. Section 2:Friction, Gravity, and Elastic Forces • What factors determine the strength of the friction force between two surfaces? • What factors affect the gravitational force between two objects? • Why do objects accelerate during free fall? • When is matter considered to be elastic?

  26. Gravity Between Objects • The force of gravity between objects increases with greater mass and decreases with greater distance.

  27. Mass and Weight • The gravitational force exerted on a person or object at the surface of a planet is known as weight.

  28. Free Fall • The graph shows how the speed of an object in free fall changes with time. Use the graph to answer the following questions.

  29. 9.8 m/s; 29.4 m/s. Interpreting Graphs: What is the speed of the object at 1 second? At 3 seconds? Free Fall

  30. The slope is 9.8. The speed increases by 9.8 m/s each second. Calculating: Calculate the slope of the graph. What does this number represent? Free Fall

  31. 58.8 m/s Predicting: Use the slope that you calculated in Step 2 to predict the object’s speed at 6 seconds. Free Fall

  32. The object’s speed increases at a constant rate. Drawing Conclusions: The graph has a constant slope. What does the slope tell you about the object’s motion? Free Fall

  33. Air Resistance • Falling objects with a greater surface area experience more air resistance.

  34. Links on Friction • Click the SciLinks button for links on friction.

  35. Free Fall • Click the Video button to watch a movie about free fall.

  36. End of Section:Friction, Gravity, and Elastic Forces

  37. Section 3:Newton’s First and Second Laws • What is Newton’s first law of motion? • What is Newton’s second law of motion?

  38. A speedboat pulls a 55-kg water-skier. The skier to accelerates at 2.0 m/s2. Calculate the net force that causes this acceleration. Read and Understand What information have you been given? Mass of the water-skier (m) = 55 kg Acceleration of the water-skier (a) = 2.0 m/s2 Calculating Force

  39. A speedboat pulls a 55-kg water-skier. The skier accelerates at 2.0 m/s2. Calculate the net force that causes this acceleration. Plan and Solve What quantity are you trying to calculate? The net force (Fnet) = __ What formula contains the given quantities and the unknown quantity? a = Fnet/m or Fnet = m x a Perform the calculation. Fnet = mxa= 55 kg x 2.0 m/s2 F = 110 kg • m/s2 F = 110 N Calculating Force

  40. A speedboat pulls a 55-kg water-skier. The skier accelerates at 2.0 m/s2. Calculate the net force that causes this acceleration. Look Back and Check Does your answer make sense? A net force of 110 N is required. This does not include the force that overcomes friction. Calculating Force

  41. Practice Problem What is the net force on a 1,000-kg object accelerating at 3 m/s2? 3,000 N (1,000 kg x 3 m/s2) Calculating Force

  42. Practice Problem What net force is needed to accelerate a 25-kg cart at 14 m/s2? 350 N (25 kg x 14 m/s2) Calculating Force

  43. More on Newton’s Laws • Click the PHSchool.com button for an activity • about Newton’s laws.

  44. End of Section:Newton’s First and Second Laws

  45. Section 4:Newton’s Third Law • What is Newton’s third law of motion? • How can you calculate the momentum of an object? • What is the law of conservation of momentum?

  46. Newton’s Third Law of Motion • Newton’s third law of motion states that if one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction on the first object.

  47. Which has more momentum: a 3.0-kg sledgehammer swung at 1.5 m/s, or a 4.0-kg sledgehammer swung at 0.9 m/s? Read and Understand What information are you given? Mass of smaller sledgehammer = 3.0 kg Velocity of smaller sledgehammer = 1.5 m/s Mass of larger sledgehammer = 4.0 kg Velocity of larger sledgehammer = 0.9 m/s Calculating Momentum

  48. Which has more momentum: a 3.0-kg sledgehammer swung at 1.5 m/s or a 4.0-kg sledgehammer swung at 0.9 m/s? Plan and Solve What quantities are you trying to calculate? The momentum of each sledgehammer = __ What formula contains the given quantities and the unknown quantity? Momentum = Mass x Velocity Perform the calculation. Smaller sledgehammer = 3.0 km x 1.5 m/s = 4.5 kg•m/s Larger sledgehammer = 4.0 km x 0.9 m/s = 3.6 kg•m/s Calculating Momentum

  49. Which has more momentum: a 3.0-kg sledgehammer swung at 1.5 m/s or a 4.0-kg sledgehammer swung at 0.9 m/s? Look Back and Check Does your answer make sense? It is possible for the 3.0-kg hammer to have more momentum than the 4.0-kg one because it has a greater velocity. Calculating Momentum

  50. Practice Problem A golf ball travels at 16 m/s, while a baseball moves at 7 m/s. The mass of the golf ball is 0.045 kg and the mass of the baseball is 0.14 kg. Which has greater momentum? Golf ball: 0.045 kg x 16 m/s = 0.72 kg•m/s Baseball: 0.14 kg x 7 m/s = 0.98 kg•m/s The baseball has greater momentum. Calculating Momentum

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