1 Speed Velocity Acceleration What is speed velocity

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

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

2 Speed is the distance traveled per unit of time. Speed (s) = distance

2 Speed is the distance traveled per unit of time. Speed (s) = distance (d) time (t) 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

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 B. Constant Speed is when the object covers equal distances in equal amounts

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

5 Four Step Approach to Solving Problems (RUBIES) Step 1 RUB Re-Read, Underline the

5 Four Step Approach to Solving Problems (RUBIES) Step 1 RUB Re-Read, Underline the question, Bracket the information and draw a picture. Step 2 I 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

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] d= t= s= Formula Plug-in Units, units! Answer

7 “A car traveled 110 miles in 2 hours. ” What is the average

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] d = 110 miles t = 2 hours s= Formula Plug-in Units, units! Answer

8 “A car traveled 110 miles in 2 hours. ” Step 3 Eliminate unnecessary

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

9 “A car traveled 110 miles in 2 hours. ” Step 3 Set up

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

10 “A car traveled 110 miles in 2 hours. ” Step 4 Solve the

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 d = 110 mi d t = 2 hours S= s = 55 mi/hr t Plug-in Answer S = 110 mi S = 55 mi/hr 2 hr Units, units!

11 Problem Set (speed)

11 Problem Set (speed)

12 Consider the problem… “A runner’s average speed during the 10 kilometer race was

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] d= t= s= [10 km] Formula Plug-in Units, units! Answer

13 “A runner’s average speed during the 10 kilometer race was 20 km/hr. What

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 d = 10 km Formula Plug-in t= s = 20 km/hr Units, units! Answer

14 “A runner’s average speed during the 10 kilometer race was 20 km/hr. What

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

15 “A runner’s average speed during the 10 kilometer race was 20 km/hr. What

15 “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 d = 10 km t = 0. 5 hr s = 20 km/hr Formula t= d s Plug-in t = 10 km (hr) 20 km/hr Units, units! Answer 10 km =0. 5 20 km/hr hr

16 Problem Set (time)

16 Problem Set (time)

17 “You decide to go to Dallas to see friends. Your friends tell you

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? ” Step 1 Re-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) d = 280 mi Formula t = 4 hr s = 70 mi/hr d=s*t Plug-in Answer d =70 mi/hr * 4 hr = 280 mi Units, units!

18 Problem Set (distance)

18 Problem Set (distance)

19 Instantaneous speed (Reading on your speedometer) and Average speed distance traveled over (Total

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

20 What is the difference between speed and velocity? r i/h m 5 5

20 What is the difference between speed and velocity? r i/h m 5 5 Velocity has speed & direction. 55 mi/hr All of these cars had different velocities because they were traveling in different directions. 55 mi /h r

21 A distance/time graph makes it possible to “see” speed. This graph shows how

21 A distance/time graph makes it possible to “see” speed. This graph shows how fast the swimmers went during their workout. d e e Which swimmer swam at a constant (the same) speed throughout her workout? p s t n a t s n Which one stopped during his/her workout? Co Is a g ai in tl e h r st Stopped here 400 meters at 10, 15, & 20 minutes

22 Make the speed graph & answer some questions

22 Make the speed graph & answer some questions

23 Acceleration

23 Acceleration

24 Acceleration is defined as the change in velocity over time. (change) in velocity

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

25 A go-cart started from the top of a hill at 5 meters per

25 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 1 Re-Read, Underline the question, Bracket the information and draw a picture. 5 m/s top Vf = V i= Formula Plug-in Answer t= a= bottom 35 m/s In 6 s

26 A go-cart started from the top of a hill at 5 meters per

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 second 6 seconds later. What was the acceleration of the go-cart? Start: initial Velocity Step 2 Identify the variables, list the symbols and data, Write down what you know and what are you trying to find acceleration = final velocity – initial velocity time Vf = 35 m/s Vi= 5 m/s Formula Plug-in Answer 6 s t= 6 s a= bottom 35 m/s Finish: final Velocity 5 m/s top

27 A go-cart started from the top of a hill at 5 meters per

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 second 6 seconds later. What was the acceleration of the go-cart? Step 3 Eliminate unnecessary data and select appropriate formula. Set up the formula. Vf - V i t Vf = 35 m/s Formula Vi= 5 m/s Vf - V i t= 6 s tf - ti a= Plug-in Answer bottom 35 m/s 6 s Final Velocity Initial Velocity 5 m/s top

28 A go-cart started from the top of a hill at 5 meters per

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 second 6 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) Vf = 35 m/s Vi= 5 m/s t= 6 s a = 5 m/s 2 Formula Vf - V i t Plug-in 35 m/s – 5 m/s 6 s Answer 30 m/s 6 s = 5 m/s 2

29 (Problem Set)

29 (Problem Set)

30 Acceleration is defined as the change in velocity over time. Any time an

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,

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 i/h m m 70 i/h 70 70 /h i m Velocity involves both

32 i/h m m 70 i/h 70 70 /h i m 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 m i / h i/h 70 m i/h

33 Think Differently About Acceleration 1. Consider a car moving at a constant speed

33 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. Constant Speed of 55 mph 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 both speed and direction).

34 Think Differently About Acceleration 5. The car is accelerating because its velocity is

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