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Speed, Velocity, Acceleration

Speed, Velocity, Acceleration. What is speed , velocity and acceleration ?. distance (d). Speed (s) =. time (t). Speed is the distance traveled per unit of time. Each variable measured by units : Distance : meters (m), miles (mi)

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Speed, Velocity, Acceleration

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  1. Speed, Velocity, Acceleration What is speed, velocity and acceleration?

  2. distance (d) Speed (s) = time (t) Speed is the distance traveledper unit of time. Each variable measured by units: Distance: meters (m), miles (mi) Time: seconds (s), hours (hr), minutes (min) Speed: meters per second (m/s), miles per hour (mi/hr), kilometers per hour (km/hr)

  3. 3 TYPES OF SPEED Instantaneous, Average, Constant Pretend you are looking at your car's speedometer while you are driving. The reading you get from your speedometer is A. instantaneous speed… This is the speed that you are traveling at that moment.

  4. d s = t distance speed = time • B. Constant Speed is when the object covers equal distances in equal amounts of time. • C. Average speed isthe total distance traveled divided by the total time. Itcan be calculated using the following formula: Average Speedis: Total distance = all distance traveled over Total time = final time (end)minus initial time (beginning) ...or shortened:

  5. Four Step Approach to Solving Problems (RUBIES) Step 1RUB Re-Read, Underline the question, Bracket the information and draw a picture. Step 2I Identify the variables, list the symbols and data, Write down what you know and what are you trying to find Step 3 E Eliminate unnecessary data and select appropriate formula. Set up the formula. Step 4 S Solve the problem, plug-in the numbers and solve. Select the correct answer (if multiple choice)

  6. Consider the problem… “A car traveled 110 miles in 2 hours.” What is the average speed of the car? Step 1 Re-Read, Underline the question, Bracket the information and draw a picture. [110 miles] [2 hours] Formula Plug-in Answer d = t = s = Units, units, units!

  7. “A car traveled 110 miles in 2 hours.” What is the average speed of the car? Step 2 Identify the variables, list the symbols and data, Write down what you know and what are you trying to find [110 miles] [2 hours] Formula Plug-in Answer 110 miles d = 2 hours t = s = ? Units, units, units!

  8. d s = t “A car traveled 110 miles in 2 hours.” Step 3Eliminate unnecessary data and select appropriate formula. Set up the formula. Formula Plug-in Answer 110 miles d = 2 hours t = s = ? Units, units, units!

  9. “A car traveled 110 miles in 2 hours.” Step 3Set up the formula. EQUATION Formula Plug-in Answer 110 miles d = d 2 hours t = S = t s = ? Units, units, units!

  10. “A car traveled 110 miles in 2 hours.” Step 4 Solve the problem, plug-in the numbers and solve. Select the correct answer (if multiple choice) 55 mi/hr Formula Plug-in Answer 110 mi d = 2 hours d 110 mi t = S = S = S = 55 mi/hr t 2 hr s = 55 mi/hr Units, units, units!

  11. Problem Set (speed)

  12. Consider the problem… “A runner’s average speed during the 10 kilometer race was 20 km/hr. What was his time?’” Step 1 Re-Read, Underline the question, Bracket the information and draw a picture. Speed of runner: [20 km/hr] [10 km] Formula Plug-in Answer d = t = s = Units, units, units!

  13. “A runner’s average speed during the 10 kilometer race was 20 km/hr. What was his time?” Step 2 Identify the variables, list the symbols and data, Write down what you know and what are you trying to find Speed of runner: 20 km/hr 10 km Formula Plug-in Answer 10 km d = ? t = 20 km/hr s = Units, units, units!

  14. d t = s d (km) t (hr) = s (km/hr) “A runner’s average speed during the 10 kilometer race was 20 km/hr. What was his time?’” Step 3Eliminate unnecessary data and select appropriate formula. Set up the formula. Formula Plug-in Answer 10 km d = ? t = 20 km/hr s = Units, units, units!

  15. d t = s “A runner’s average speed during the 10 kilometer race was 20 km/hr. What was his time?’” Step 4 Solve the problem, plug-in the numbers and solve. Select the correct answer (if multiple choice) Time: 0.5 Hour Formula Plug-in Answer 10 km d = 1 r 10 km 0.5 hr 10 km t = t (hr) 0.5hr = = 20 km/hr 20 km/hr 20 km/hr s = Units, units, units!

  16. Problem Set (time)

  17. “You decide to go to Dallas to see friends. Your friends tell you that it takes 4 hours to get to Dallas at an average speed of 70 miles per hour. Approximately how many miles is it to their house?” 70 miles per hour Step 1Re-Read, Underline the question, Bracket the information and draw a picture. Step 2 Identify the variables, list the symbols and data, Write down what you know and what are you trying to find ? Step 3 Eliminate unnecessary data and select appropriate formula. Set up the formula. Step 4 Solve the problem, plug-in the numbers and solve. Select the correct answer (if multiple choice) Formula Plug-in Answer 280 mi d = 4 hr d = s * t t = = 280 mi d =70 mi/hr * 4 hr 70 mi/hr s = Units, units, units!

  18. Problem Set (distance)

  19. Instantaneous speed(Reading on your speedometer) • and Average speed (Total distance traveled over total time) • Both do not involve direction.

  20. What is the difference between speed and velocity? 55 mi/hr Velocity has speed &direction. 55 mi/hr All of these cars had different velocitiesbecause they were traveling in different directions. 55 mi/hr

  21. A distance/time graph makes it possible to “see” speed. A distance/time graph makes it possible to “see” speed. This graph shows how fast the swimmers went during their workout. This graph shows how fast the swimmers went during their workout. Which swimmer swam at a constant (the same) speed throughout her workout? Constant speed Is a straight line Which one stopped during his/her workout? Stopped here 400 meters at 10, 15, & 20 minutes

  22. Make the speed graph & answer some questions

  23. Acceleration

  24. (change) in velocity acceleration = (change) time final velocity – initial velocity acceleration = final time – initial time Vf - Vi V = a = tf - ti t Acceleration is defined as the change in velocity over time.

  25. Formula Plug-in Answer A go-cart started from the top of a hill at 5 meters per second. At the bottom of the hill it ended up with a speed of 35 meters per second 6 seconds later. What was the acceleration of the go-cart? Step 1Re-Read, Underline the question, Bracket the information and draw a picture. 5 m/s top Vf = In 6 s Vi= t = a = bottom 35 m/s

  26. A go-cart started from the top of a hill at 5 meters per second. At the bottom of the hill it ended up with a speed of 35 meters per second6 seconds later. What was the acceleration of the go-cart? Formula Plug-in Answer Start: initialVelocity Step 2 Identify the variables, list the symbols and data, Write down what you know and what are you trying to find 5 m/s top final velocity – initial velocity acceleration = time 35 m/s Vf = 6 s Vi= 5 m/s t = 6 s ? a = bottom Finish: final Velocity 35 m/s

  27. A go-cart started from the top of a hill at 5 meters per second. At the bottom of the hill it ended up with a speed of 35 meters per second6 seconds later. What was the acceleration of the go-cart? Vf - Vi t InitialVelocity Step 3 Eliminate unnecessary data and select appropriate formula. Set up the formula. 5 m/s top 35 m/s Vf = Formula Plug-in Answer 6 s Vi= 5 m/s Vf - Vi t = 6 s tf - ti ? a = bottom Final Velocity 35 m/s

  28. A go-cart started from the top of a hill at 5 meters per second. At the bottom of the hill it ended up with a speed of 35 meters per second6 seconds later. What was the acceleration of the go-cart? Step 4 Solve the problem, plug-in the numbers and solve. Select the correct answer (if multiple choice) 35 m/s Vf = Formula Plug-in Answer Vi= Vf - Vi 35m/s– 5 m/s 5 m/s 30 m/s = 5 m/s2 6 s t = t 6 s 6s a = 5 m/s2

  29. (Problem Set)

  30. Acceleration is defined as the change in velocity over time. Any time an object's velocity is changing, we say that the object is accelerating. This brings up an important point. In common language, when things speed up, we say that they are "accelerating," and, when they slow down, we say that they are "decelerating."

  31. However, in the language of physics, we say that both objects are accelerating, not because both objects are speeding up, but because both objects have changing velocities. • POSITIVE (+) ACCELERATION (SPEEDING UP) • NEGATIVE (-) ACCELERATION (DECELERATING) SLOW DOWN

  32. 70 mi/h 70 mi/h 70 mi/h Velocity involves both speed and direction. Changing velocity does not have to necessarily involve a change in speed. It could just involve a change in direction. 70 mi/h 70 mi/h 70 mi/h

  33. Constant Speed of 55 mph Think Differently About Acceleration 1. Consider a car moving at a constant speed of 55 mph while turning in a circle. 2. The car's velocity is not constant, even though the speed is constant. 3. WHY? This is because the direction of motion is constantly changing while the car is turning around the track. 4. Since the direction is changing, even though the speed is not, the velocity is changing (velocity involves bothspeed and direction).

  34. Think Differently About Acceleration Constant Speed of 55 mph 5. The car is accelerating because its velocity is changing. 6. As a result, the car is accelerating, even though it is neither speeding up nor slowing down.

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