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FORCES AND MOTION

FORCES AND MOTION. New Car Crash Compilation Video 2011- Youtube. http://www.youtube.com/watch?v=jko6qzsOvgg. WHAT IS A FORCE?. A force is simply a push or a pull. THERE IS A BIG RELATIONSHIP BETWEEN FORCE AND MOTION. WITHOUT A FORCE THERE WOULD BE NO MOTION. Forces.

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FORCES AND MOTION

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  1. FORCES AND MOTION

  2. New Car Crash Compilation Video 2011- Youtube http://www.youtube.com/watch?v=jko6qzsOvgg

  3. WHAT IS A FORCE? A force is simply a push or a pull. THERE IS A BIG RELATIONSHIP BETWEEN FORCE AND MOTION WITHOUT A FORCE THERE WOULD BE NO MOTION.

  4. Forces • What types of forces can you think of? • How is the object affected by those forces?

  5. Examples of forces acting on objects would be: A flag being blown by the force of the wind. A jet engine propelling an airplane forward. Iron being pulled toward a magnet.

  6. Examples of forces acting on objects would be: Opening and closing a door. A space shuttle lifting off

  7. What type of force would these objects need to move? kites Sports equipment wagons sleds

  8. FORCES ALWAYS OCCUR IN PAIRS Forces give an object the energy to move, stop moving, or change direction.

  9. Vocabulary InstructionsMake a Frayer’s Model Box for EACH of the words below: • Force • Net Force • Unbalanced Force • Balanced Force • Friction 6. Motion 7. Reference Point 8. Speed 9. Average Speed 10. Velocity 11. Acceleration

  10. Net Force • Total amount of force acting on an object. • Will also determine motion and direction of motion.

  11. Net Force • Total amount of force acting on an object. • Will also determine motion and direction of motion.

  12. Net Force • The total amount of forces acting on an object. • When the forces are acting in the opposite direction you subtract the forces.

  13. Net Force • Total amount of force acting on an object. • When forces are acting in the same direction you add the forces together to get the net force.

  14. HOW DOES FORCE CAUSE MOTION? Motion is a result of UNBALANCED FORCES. UNBALANCED FORCE is when the net force on an object is greater than 0.

  15. HOW DO UNBALANCED FORCES CAUSE MOVEMENT? REMEMBER: Forces always come in pairs. 2 Unbalanced forces acting in the same direction get added together and cause motion.

  16. EXAMPLESOF UNBALANCED FORCES PUSHING A SHOPPING CART SKIING DOWNHILL

  17. WHAT IS A BALANCED FORCE? Balanced Forces cause no motion. = when the net force on an object is zero. The paired forces occur in opposite directions and are of equal force.

  18. EXAMPLES OF BALANCE FORCE There is an equal amount of people playing tug of war.

  19. WHICH PICTURES SHOW BALANCED FORCE? WHICH PICTURES SHOW UNBALANCED FORCE?

  20. FRICTION : FORCE THAT OPPOSES MOTION Friction - The force that opposes motion between two surfaces. • Friction occurs because all surfaces are covered with microscopic hills and valleys, which make the surface rough. • When surfaces touch, the hills and valleys stick to each other and this causes friction even if the surfaces look smooth.

  21. Humans have tiny ridges in their hands and feet which increase the amount of friction. This allows us to clasp objects and avoid slipping. Tires are designed to increase friction on the road. HOW DO THEY DO THIS?

  22. FACTORS THAT AFFECT THE AMOUNT OF FRICTION 1. Roughness - The more rough the surface; more friction created. 2. Force - The more force pushing the object; the more friction between valleys. 3. Attraction between objects(static) - The greater the attraction; the more friction created.

  23. Would you rather catch a ball diving in the grass or on concrete? Why do ice skates only have a small blade? Why put oil in your car? Why can’t you open a jar with lotion on your hands? All of these questions deal with friction !!!!!

  24. The rougher the surface, the ________ the friction. • If the force is increased, the hills and valleys of the surfaces can come in closer contact so friction is _______________. • Less massive objects exert less force on surfaces than more massive objects so friction is _______.

  25. TYPES OF FRICTION 1. Sliding Friction 2. Rolling Friction 3. Fluid Friction

  26. SLIDING FRICTION Definition - Friction caused by objects sliding across one another. Examples - Pushing an object (dresser), sledding, brakes, chalk

  27. ROLLING FRICTION Definition - Friction produced by objects such as wheels or ball bearings. Examples - Wheels are placed under objects to reduce sliding friction. Cars, moving large objects with dollies,

  28. FLUID FRICTION Definition - Force exerted by a fluid(gas and liquids). Examples - Water, oil, and air. Sliding friction is usually changed to fluid friction by adding lubricants. Why is it on a slick floor?

  29. STATIC FRICTION Definition - When a force is applied, but the object does not move. Examples - Block and a table. Block will move when the force is large enough to overcome the friction.

  30. WAY FRICTION IS HELPFUL 1. Push against car to make it move. 2. Brakes to stop objects. 3. Between pencil and paper. 4. Friction between floor and feet.

  31. WAYS FRICTION CAN BE HARMFUL 1. Friction in the engine causes temperature to rise. 2. Wind and water causes erosion. 3. Holes in you jeans. 4. Hard to move heavy objects.

  32. WAYS TO REDUCE FRICTION 1. Lubricant(liquid or gas) 2. Wheels 3. Ball bearings 4. Make surfaces that rub against each other smoother.

  33. WAYS TO INCREASE FRICTION 1. Make surface rougher(sand on ice or batters glove). 2. Increase the force pushing the surfaces together.

  34. Name the different types of friction. Give examples of each.

  35. Name two ways friction is helpful and harmful.

  36. Name two ways to overcome friction.

  37. WHAT IS MOTION? Motion is a change in an objects position over time when compared with a reference point.

  38. Reference pointor frame of reference is the background or object that appears to stay in place when compared to an object being observed in motion. ***Most common reference point is the Earth’s surface.*** Other reference points are buildings, trees, mountains etc. What reference point do the balloonists use?

  39. Reference Point

  40. Motion is not absolute, it depends on the observer. For example, if Jack and Jill are sitting in a bus, Jack sees Jill at rest and Jill sees Jack at rest. BUT, if we zoom out, we see that Jack and Jill are sitting on a bus moving at a constant speed of 25mph. From the reference INSIDE the bus, Jack sees Jill at rest and Jill sees Jack at rest.

  41. Jill’s mother, waiting for the bus, sees Jill’s bus go by at 25mph. She sees Jill traveling 25mph. Jack on the other hand, still sees Jill as going 0mph. What they observe seems to depend on their reference point.

  42. While riding the bus, Jill begins throwing cookies to Jack. Jill can throw cookies at a speed of 30 mph. From their reference point, Jack and Jill both see the cookies going 30mph.

  43. As Jill’s mom observes the cookie tossing from where she is standing on the side of the road, she sees the cookies going 30mph on a bus moving 25mph in the same direction. SO, she observes the cookies going 55mph!!!!!!

  44. As Jill continues to throw 30mph cookies at Jack, the bus drives by Jack’s mom on a bicycle. She is riding 10mph in the same direction as the bus is traveling 25mph. From her point of reference, Jack seems to only be going 15mph (25mph – 10mph) and she see the tossed cookies going 45mph (15mph + 30mph).

  45. As the cookie tossing between Jack and Jill continues, a car drives by going 40mph in the other direction. The observer in the car sees Jack going 65mph (40mph + 25mph). The observer then notices the flying cookies to be traveling a whopping 95mph!!!!!! (40mph + 25mph + 30mph).

  46. Types of Motion • Projectile Motion: the curved path an object follows when thrown near the surface of the Earth.

  47. Types of Motion • Centripetal Motion: when an object moves in a circular path. • Ex: Moon in centripetal motion as it revolves around the Earth.

  48. SO WHAT IS SPEED? Speed is the rate at which an object moves.This is determined by the distance traveled and the time it takes to travel. SO… SPEED = DISTANCE / TIME UNITS FOR SPEED: meters per sec (m/s) miles per hour (mi/hr), feet per sec (ft/s)

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