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Forces and Motion

Chapter 12 . Forces and Motion. Page 356-362. 12.1 Forces. Can cause a resting object to move. It can accelerate a moving object by changing the object’s speed or direction. SI unit = N (for newton). May the Force be with you Yoda.

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Forces and Motion

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  1. Chapter 12 Forces and Motion

  2. Page 356-362 12.1 Forces

  3. Can cause a resting object to move. It can accelerate a moving object by changing the object’s speed or direction. SI unit = N (for newton) May the Force be with you Yoda

  4. One N is the force that can cause a 1-kg mass to accelerate at a rate of 1 m/s2 N = 1kg x m/s2 Newton (not the cookie)

  5. Balanced Forces • Has a net force of 0 • No change in object’s motion. • IE: Two Sumo wrestlers of equal weight. Locked head to head and neither one is moving.

  6. Unbalanced Forces • Net force acting on an object is not equal to 0 • Object is put into motion and accelerates. • IE: Two sumo wrestlers not equal in weight.

  7. 3 types • Static • Sliding • Rolling What the Fric…. tion These 2 symbols mean just listen and look no need to take notes as it will not be tested or it will be shown in the lecture at a later time.

  8. Static Friction • Force that acts on an objects that are NOT moving. • Acts in the direction opposite to that of the applied force. • IE: You pushing on a world’s largest watermelon that weight 2 tons.

  9. Sliding Friction • Force that opposes the direction of motion of an object as it slides over a surface. • IE: You pushing on a really big box of watermelons.

  10. Rolling Friction • Force that acts on rolling objects. • Object is bent slightly out of shape. • IE: You pushing a shopping cart full of watermelons….or a little kid you want to terrorize.

  11. Gravity • Force that acts between any 2 masses. • Attractive force that pulls objects together. • Can act over large distances.

  12. Let’s quiz your learning

  13. What amount of force accelerates a 1-kilogram mass at 1 m/s2? • 0.1 newton • 1 newton • 10 newtons • 100 newtons

  14. What amount of force accelerates a 1-kilogram mass at 1 m/s2? • 0.1 newton • 1 newton • 10 newtons • 100 newtons

  15. What is the net force acting on the rope? • The answer depends upon the mass of the two groups of people. • The answer depends upon the mass of the rope. • The answer depends upon the length of the rope. • zero

  16. What is the net force acting on the rope? • The answer depends upon the mass of the two groups of people. • The answer depends upon the mass of the rope. • The answer depends upon the length of the rope. • zero

  17. What is the net force of a pair of balanced forces? • the sum of the forces • the product of the forces • zero • 1 newton

  18. What is the net force of a pair of balanced forces? • the sum of the forces • the product of the forces • zero • 1 newton

  19. Because the boulder is at rest, what do you know about the net force acting on it? • The net force is positive. • The net force is negative. • The net force is decreasing. • The net force is zero.

  20. Because the boulder is at rest, what do you know about the net force acting on it? • The net force is positive. • The net force is negative. • The net force is decreasing. • The net force is zero.

  21. Can you answer these questions?

  22. Plant 1

  23. scale

  24. rope

  25. Plant 2

  26. Page 356-362 End of - - - 12.1 Forces

  27. Page 363-369 12.2 Newton’s 1st and 2nd Law of Motion

  28. Newton's First Law of Motion • The state of motion of an object does not change as long as the net force acting on the object is zero

  29. inertiathe tendency of an object to resist a change in its motion. Vocabulary In other words, an object at rest tends to remain at rest, and an object in motion tends to remain in motion with the same direction and speed. View 1:52 clip

  30. The acceleration of an object is equal to the net force acting on it divided by the object's mass . Newton's second law of motion Video clip to “get it” run time 1:45

  31.   An automobile with a mass of 1000 kilograms accelerates when the traffic light turns green. If the net force on the car is 4000 newtons, what is the car's acceleration? Newton's Second Law What information are you given? M= 1000kg F= 4000N (in the forward direction) A = ?

  32. USE FORMULA AND REPLACE What information are you given? M= 1000kg F= 4000N (in the forward direction) a = Net force then, 4000N = 4N = 4m/s2 Mass 1000kg kg

  33. Weight and Mass Weight (W) is substituted for force (F) Acceleration due to gravity (g) is substituted for acceleration (a). In other words, W = mg is a different form of So when the equation is solved for force, F = ma. The value of g in the formula is 9.8 m/s2.

  34. An astronaut with a mass of 88 kg weighs 863 N on Earth. An astronaut with a mass of 88 kg weighs 141 N on the moon. Which of these astronauts “weighs” more?

  35. They are the same!

  36. An astronaut with a mass of 88 kg weighs 863 N on Earth. An astronaut with a mass of 88 kg weighs 141 N on the moon. Remember: Weight is a measure of the force of gravity acting on an object!!

  37. Let’s quiz your learning

  38. How does a zero net force affect an object's motion? • The velocity increases. • The velocity decreases. • The direction changes. • The motion does not change.

  39. How does a zero net force affect an object's motion? • The velocity increases. • The velocity decreases. • The direction changes. • The motion does not change.

  40. Which objects and devices absorb the energy of the crash? • the crushing of the car's body • the air bag • the seatbelt • all of the above

  41. Which objects and devices absorb the energy of the crash? • the crushing of the car's body • the air bag • the seatbelt • all of the above

  42. 33.0 N 330 N 33.0 kg 330 kg If the astronaut in the photo stood on Mars where the acceleration due to gravity is about 3.7 m/s2, how much would the astronaut weigh?

  43. 33.0 N 330 N 33.0 kg 330 kg If the astronaut in the photo stood on Mars where the acceleration due to gravity is about 3.7 m/s2, how much would the astronaut weigh?

  44. The two-cart chain would accelerate at half the rate of the single cart. The two-cart chain would accelerate at twice the rate of the single cart. The single cart would accelerate at half the rate of the two-cart chain. They would accelerate at the same rate. How would the acceleration of a chain of two carts compare with the acceleration of a single cart if the same force acted on both?

  45. The two-cart chain would accelerate at half the rate of the single cart. The two-cart chain would accelerate at twice the rate of the single cart. The single cart would accelerate at half the rate of the two-cart chain. They would accelerate at the same rate. How would the acceleration of a chain of two carts compare with the acceleration of a single cart if the same force acted on both?

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