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Chapter 1

Chapter 1. Motion. Opening Question. How fast am I moving right now? Did you take into account the… plate shifting (1 in/yr) earth rotating (1038 mph) earth orbiting (67000 mph) galaxy spinning (43000 mph) universe expanding. Motion. How do we determine how fast something moves?.

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Chapter 1

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  1. Chapter 1 Motion

  2. Opening Question • How fast am I moving right now? • Did you take into account the… • plate shifting (1 in/yr) • earth rotating (1038 mph) • earth orbiting (67000 mph) • galaxy spinning (43000 mph) • universe expanding

  3. Motion • How do we determine how fast something moves? • Create a reference point because everything moves relative to everything else • All based on your perspective or point of view (POV)

  4. From Your POV • You are in a car on I-5 going exactly 70 mph. How fast is...

  5. Motion • How do we measure “fastness”? • Speed – the rate at which something moves • Rate – how much in a certain amount of time • Ex. mph, kph, or m/s

  6. Rates • Max is thinking about different units that can be used to express the speed of a car on a highway. Which units couldn’t be used to express the speed of a car?

  7. BugattiVeyron Super Sport(Fastest Car in the World)

  8. Motion • What is the difference between instantaneous and average speed? • Instantaneous is at a specific point in time • Average is over a length of time • Average speed is the distance traveled (displacement) divided by time • Units: m/s or km/hr

  9. Speed (Math Triangle)

  10. BugattiVeyron - Practice • If the car went 2875 m in 25 s, what is its average speed? • If the car was going 115 m/s, how fast can it cover 500 m? • If the car was going 115 m/s how far does it go in 2 s? • Speed = 115 m/s • 258 mph • Time = 4.3 s • Distance = 230m

  11. Speed – Basic Practice • What is the speed of a bike that travels 15 m in 2 s? • If a rabbit is going 3 m/s for 4 s, how far did it go? • How long did it take a koala bear moving at 0.5 m/s to climb a 20 m tree? • 7.5 m/s • 12 m • 40 s

  12. Speed – Advanced Practice • How much time would it take for the sound of thunder to travel 1,500 meters if sound travels at a speed of 330 m/sec? • 4.5 s • How much time would it take for an airplane to reach its destination if it traveled at an average speed of 790 kilometers/hour for a distance of 4,700 kilometers? • 5.9 hr • How far can a person run in 15 minutes if he or she runs at an average speed of 16 km/hr? (HINT: Remember to convert minutes to hours.) • 4 km

  13. Speed – Advanced Practice • The speed of light is about 3.00 x 105km/s. It takes approximately 1.28 seconds for light reflected from the moon to reach Earth. What is the average distance from Earth to the moon? • 384000 km • The average distance from the sun to Pluto is approximately 6.10 x 109km. How long, in hours, does it take light from the sun to reach Pluto? Use the speed of light from the previous question to help you. • 5.6 h (which is 20000 s OR 333.3 min)

  14. Velocity • What is the difference between speed and velocity? • Velocity is speed, but with a direction • Show direction by using: • Arrows • Cardinal directions • + or -

  15. Velocity • Why is it called a speedometer and not velocitiometer? • It does not give you a direction, only a speed • Unless its combined with a compass or GPS

  16. Constant • If a car is driving 60 mph in a circle, does it have a constant velocity or speed? • Constant means it doesn’t change • The direction is changing, so it only has constant speed

  17. Constant If a car has a constant velocity of 30 m/s does it have a constant speed? Yes, it will continue going 30 m/s.

  18. Constant • If a car is going a constant speed of 25 m/s does it have a constant velocity? • No, constant speed does not mean constant direction

  19. Distance-Time Graphs

  20. Motion • Identify which of the following are examples of acceleration.

  21. Motion What is acceleration? • Acceleration – the rate at which velocity changes • Has direction (+ or - ) • Units: m/s2 • vf = final velocity • vi = initial velocity • t = time

  22. Acceleration A bike goes from rest to 20 m/s in 5 s, what is the acceleration? A runner going 10 m/s comes to a stop after 5 seconds, what was the acceleration? • 4 m/s2 • Positive = speed up • Same direction as v • -2 m/s2 • Negative = slow down • Opposite direction as v • Still accelerating! (not deceleration)

  23. Acceleration What is your acceleration when you have a constant velocity? Any velocity minus itself is zero, so the acceleration would be zero You are not going faster or slower

  24. Motion Combined • If a truck at rest goes to 50 m/s in a northerly direction in 10 seconds, what is the truck’s: • Speed? • Velocity? • Acceleration? Speed = 50 m/s Velocity = 50 m/s north Acceleration = 5 m/s2(north)

  25. Motion Combined – Practice • The cheetah, the fastest of land animals, can run a distance of 274 m in 8.65 s at its top speed. What is the cheetah’s top speed? • Answer = 31.7 m/s • In 1985, Matt Biondi set a record for the men’s 100 m freestyle event in swimming. It took him 49.17 s to swim the 100 m length of the pool. What was his speed? • Answer = 2.0 m/s • While drag racing out of our school parking lot, I time myself at a speed of 40 m/s, which was 7 s after starting. What was my acceleration during this time? • Answer = 5.7 m/s2 • A baseball is pitched with a speed of 35 m/s. How long does it take the ball to travel 18.4 m from the pitcher’s mound to home plate? • Answer = 0.53 s

  26. Acceleration Review NO • Identify which of the following are examples of acceleration. NO YES YES YES YES

  27. BugattiVeyronvs.EuroFighter(Jet)

  28. Wooden Ball Golf Ball Metal Ball

  29. Falling Motion • What does it mean to free fall? • An object falling under the influence of gravity ONLY!

  30. Falling Motion Why can’t an object free fall in our atmosphere? Air resistance acts against gravity which prevents free fall A vacuumis the scientific term for no atmosphere

  31. Falling Motion Does everything fall at the same rate? What prevents some objects from attaining 10 m/s2 when falling? • It should and we call this the acceleration due to gravity • g = 10 m/s2 • Mass doesn’t matter! • Air resistance • Ex. Feather vs. Hammer

  32. Feather vs. Hammer (Moon)

  33. Falling Motion What is the formula for calculating the velocity of a falling object? If a baseball has been falling for 3 s, what is its velocity? • v = gt • g = 10 m/s2 • t = elapsed time (how long it has been) • 30 m/s (down)

  34. Falling Motion What is the formula for calculating how far (distance) an object has fallen? If a dead bird has fallen for 4 seconds, how far has it fallen? d = (½)gt2 g = 10 m/s2 t2 = elapsed time squared d = (1/2)(10)(4)2 d = (1/2)(10)(16) d = 80 m

  35. Falling Motion A bird was flying above your head and crapped. The crap fell 13 s before hitting your head. Crap, like everything else, falls at 10 m/s2. How fast did the crap fall right before it hit you? How far did the crap fall? v = 130 m/s d = 845 m

  36. Falling Motion • Wile E. Coyote dropped an anvil off a cliff. • What is the velocity and the traveled distance of the anvil after 3.5 s, 6 s and 15 s? • If the cliff is 3000 m high, how long will it take to hit the ground? • 35 m/s down and 61 m • 60 m/s down and 180 m • 150 m/s down and 1125 m • 24.5 s

  37. Falling Motion – Stratos Jump

  38. Wooden Ball Golf Ball Metal Ball YES

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