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Motion

Motion. Motion. Motion Occurs when an object changes position relative to a reference point Don’t have to see it move to motion took place. Motion. Distance Describes motion How far did the object move? SI unit is the meter (m) Distance vs Displacement. Displacement

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Motion

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  1. Motion

  2. Motion • Motion • Occurs when an object changes position relative to a reference point • Don’t have to see it move to motion took place

  3. Motion • Distance • Describes motion • How far did the object move? • SI unit is the meter (m) Distance vs Displacement • Displacement • Distance and direction of an object’s change in position from the starting point

  4. Speed • Speed • Distance an object travels per unit of time • Speed = distance ÷ time • s = d/t • Unit of measurement is meters/second (m/s)

  5. Speed Formula = Speed

  6. Speed Word Problems SPEED = d/t TIME = d/s DISTANCE = s x t 1. If a car travels 400m in 20 seconds, how fast is it going? 2. How long did it take you to walk 100 meters if your speed is 2 m/s? 3. What is the distance traveled if you walk 1.5 m/s in 45 seconds?

  7. Average Speed • Average Speed • Describes speed that’s changing • Total distance ÷ total time • S = d/t

  8. Instantaneous Speed • Instantaneous Speed • Speed at a given point in time • Measured by speedometers

  9. Velocity • Velocity • Speed and the direction of an object • Velocity = distance ÷ time • How are speed and velocity different? • Speed and Velocity

  10. Distance/Time Graph

  11. Acceleration • Acceleration • Rate of change of velocity (speed and direction) • Speeding up, slowing down and changing directions • Can be positive (+) or negative ( - ) • SI unit = m/s 2

  12. Acceleration Formula • A = acceleration • Vf = final velocity • Vi = initial velocity • T = time

  13. Acceleration Problems 1. A cars velocity changes from o m/s to 30 m/s in 10 seconds. Calculate acceleration. 2.If a speeding train hits the brakes and it takes the train 39 seconds to go from 54.8 m/s to 12 m/s what is the acceleration? 3. (Be careful!) How long will it take a car to go from 0 to 44 km/hr if they are accelerating at 5 km/hr2? 4. In 1970, Don “Big Daddy” Garlits set what was then the world record for drag racing. He started at rest and accelerated at 16.5 m/s² (about 1.68 times free-fall acceleration) for 6.5 s. What was Garlits’s final speed?

  14. Motion and Force • Force • Push or a pull OR Does every force produce motion??

  15. Force • Net Force • Sum of two or more forces acting on an object • Balanced Force • No motion • Unbalanced Force • Motion

  16. Inertia • Inertia • The tendency of an object to resist any change in its motion • In motion, wants to stay at same speed and in same direction • At rest, wants to stay at rest

  17. Newton’s First Law of Motion • Newton’s 1st Law • Object moving at a constant velocity keeps moving at that velocity unless an unbalanced force acts upon it • Law of Inertia • What are the unbalanced forces acting on the baseball that changes its motion?

  18. Newton’s First Law • In other words . . . • An object in motion stays in motion, an object at rest stays at rest, unless acted on by an unbalanced force

  19. Why do we wear seatbelts?

  20. Newton’s Second Law of Motion • Newton’s 2nd Law • The acceleration of an object is in the same direction as the net force and is inversely proportional to its mass • Shows relationship between force, mass and acceleration

  21. Newton’s Second Law of Motion • In other words . . . • An object will accelerate in the same direction as the force • The more massive an object, the slower it accelerates • The less massive, the faster it accelerates

  22. Newton’s Second Law of Motion

  23. Newton’s Second Law of Motion Force = Mass x Acceleration

  24. Standard Units of Force • Force • Measured in Newtons (N) • 1 Newton = 1 Kg m/s2 • Mass in Kg • Acceleration in m/s2

  25. What exactly is a Newton? 0.2248 pounds = 1 Newton of force 1 kN = 224.8 lbs of force 4 Physical Science books=100 Newtons Jumbo jet = 3.4 million Newtons 150 pound person= about 668 Newtons

  26. Newton’s Second Law Word Problems • If the mass of a helicopter is 4,500 kg and the net force on it is 18,000 N, what is the helicopter’s acceleration? • What is the net force on a dragster with a mass of 900 kg if its acceleration is 32 m/s2? • A car is being pulled by a tow truck. What is the car’s mass if the net force on the car is 3,000 N and it has an acceleration of 2.0 m/s2?

  27. Forces • 3 forces that oppose motion • Friction • Air Resistance • Gravity

  28. Friction • Friction • force that opposes motion of two surfaces that are touching • Friction • 3 types of friction • Static • Sliding • Rolling

  29. Static Friction • Static Friction • Force that prevents two surfaces from sliding • No motion • Caused by microwelds between two surfaces

  30. Sliding Friction • Sliding Friction • Force that opposes the motion of two surfaces sliding past each other • Microwelds break and reform • Slows down motion

  31. Rolling Friction • Rolling Friction • Force between a rolling object and the surface • Slows down motion

  32. Friction What would happen if we had no frictional force between objects?

  33. Air Resistance • Air Resistance • Opposes motion of objects that move through the air • Depends on speed, size, and shape of object

  34. Terminal Velocity • Terminal Velocity • Falling at a constant speed • Highest speed a falling object will reach • Depends on size, shape and mass of object

  35. Gravity • Gravity • Attractive force between two objects • Depends on • Masses of objects • Distance between them • Isaac Newton formulated Law of Universal Gravitation

  36. Gravity • Gravitational Acceleration • Without air resistance, everything falls to Earth at 9.8 m/s2 • So, acceleration due to gravity (g) = 9.8 m/s2 • Force of gravity (N) = mass (kg) x acceleration of gravity (m/s2) • F = m x g

  37. Weight • Weight • Gravitational force exerted on an object • Weigh less on the moon • Weight (N) = mass (kg) x acceleration of gravity (m/s2) • W = m x g

  38. Mass Vs. Weight • What is the difference in mass and weight? mass – amount of matter an object contains weight- force of gravity on an object

  39. Centripetal Force • Centripetal Acceleration • Acceleration toward the center of a curved path • Centripetal Force • Net force exerted toward the center of a curved path

  40. Newton’s Third Law of Motion • Newton’s 3rd Law • For every action, there is an equal and opposite reaction

  41. Newton’s Third Law of Motion

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