1. Speed, Velocity, and Acceleration
An Interactive Power Point

2. Speed To calculate speed use the equation: Speed = distance time
Speed only gives distance and time

3. Speed Units m/s km/s m/h km/h
When you read the first unit, you say meters “PER” second.
Do not write mps

4. Average Speed
On a trip from Chicago to Texas could you stay the same speed?
You could get an average of all the speeds during the trip.

5. How do we calculate average speed?
The total distance of the trip divided by the total time of travel.

6. Magic Triangle
This triangle tells you the formulas you need for speed, distance, and time
s = d t
d = s x t
t = d s

7. Speed Problems A baseball moves 11 m in 1 sec. What is its speed?
Speed = distance
time
A car travels 70 km in 1.75 h (hours). What is its speed?
S = D T

8. Speed is Relative!
What does it mean when we say that a car moves at a rate of 80 km/h?
What do we mean that it is relative to?
Unless the problem says something else, the motion that we discuss is ALWAYS relative to Earth.

9. What is Velocity? Describes the motion and the direction.
Even if speed remains the same, if the direction changes then the velocity has changed.

10. Follow the steps to solve an equation.
Problem: You walk 5 meters in 3 seconds. What is your velocity?
Step 1: Write what you know.
d = 5 meters
t = 3 seconds
v = ?
Step 2: Write the formula you will use. v = d / t
Step 3: Put the numbers in for the variables that you know.
v = 5 meters
3 seconds
Step 4: Do the math.
v = meters/seconds = 1.7m/s
Your velocity is 1.7 meters per second.

11. Equations for Speed and Velocity
v = d t
d = v  t
t = d v
You can replace the s(speed) in the triangle for v(velocity)

12. Calculating Average Speed / Velocity
d= distance
v= speed / velocity
t= time

13. Sample Speed / Velocity Problems
A car travels a distance of 16 m in 1.8 seconds. What is it’s speed?
d = 16 m
t = 1.8 s
v = ?
v = d t
v = 16m
1.8 s
v = 8.89 m/s

14. Sample Speed / Velocity Problems
Sound travels at a speed of 330 m/s. If a lightning bolt strikes the ground 1 km away from you, how long will it take for the sound to reach you?
v = 330m/s
d = 1km
t = ?
t = d v
t = 1km
330m/s You must change the km to m
t = 1000m Kids Haven’t Died By Doing Crazy Metric
330m/s
t = 3.03 s

15. Practice Problems
1.   Calculate the speed of a dog running through a field if he is covering 23.7 meters in 54 seconds.
2.   If a cross country runner covers a distance of 347 meters in 134 seconds what is her speed?
3.   What is the speed of a baseball that travels 49 meters in 2.4 seconds?

16. Practice Problems
4.   What is the speed of a horse in meters per second that runs a distance of 1.2 miles in 2.4 minutes?  
5.   Calculate the velocity of a car that travels 556 kilometers northeast in 3.4 hours.  Leave your answer in kilometers per hour.
6.   If the distance covered by a jogger is 2,541meters through the park and the time it took to cover that distance was 43.6 minutes, what was the speed of the jogger?

17. Practice Problems
7.   Which object has a greater velocity, a ball rolling down a 3.4 meter hill in six seconds or a fish swimming upstream and covering 5.4 meters in 0.4 minutes?
8.   If Seneca decides to walk across town to a store that is .95 kilometers away and she has only 25 minutes to get there, what speed does she need to maintain to arrive on time?
9.   If a projectile flies north 387 meters in 5.8 seconds, what is its velocity?
10.   Calculate the velocity of a mountain climber if that climber is moving northeast at a pace of 1.6 km in 1.4 hours?  Give your answer in the SI unit for velocity.

18. Acceleration

19. What is Acceleration? The rate of change of velocity.
Car commercial  0 to 60 mph in 10 seconds.
Speeding up
The amount of change of velocity in a time interval.

20. Acceleration The rate at which velocity changes Acceleration is:
Increasing speed
Decreasing speed
Changing direction

21. How do you measure a change?
The water was at 50m and it rose to 100m. What is the change?
We started at 9:00am and the class was over at 11:00am. What is the change?
The dog grew from 8 lbs to 15 lbs. What is the change?
We had 20 gallons, and now we have 5. What is the change?

22. Increasing speed Increase in speed = increase in acceleration
Ex—a car moving from a stopped position

23. Decreasing speed
Decrease in speed = deceleration (negative acceleration)
Ex– a car decelerates as it stops at a red light

24. Changing direction
Any change in direction is considered acceleration, even if the object’s speed remains constant
Ex– a Ferris wheel accelerates because it moves in a circle (changes direction).
Its speed is constant

25. Calculating Acceleration
Calculate the change in velocity during each unit of time
Acceleration = final velocity – initial velocity
final time – initial time OR
change in velocity (speed)
time it took for change

26. How to Calculate Acceleration?
means “change in”

27. How do you calculate Δv?
The change in velocity = the final velocity – the initial velocity.
Δv = vf – vi
You are stopped at a red light. When it turns green, you speed up to 45m/s. What is your change in velocity?
vi = 0m/s
vf = 45m/s
Δv = ?
Δv = vf-vi = 45m/s- 0m/s = 45m/s

28. Velocity is measured in meters/second
Acceleration is measured in meters per second per second or m/s2
Acceleration = 22 m/s – 4 m/s
3 s
A= 18 m/s
A = 6 m/s/s or 6m/s2

29. Let’s Practice with some Problems
A car’s velocity changes from 0 m/s to 30 m/s in 10 seconds. Calculate the car’s average acceleration.
Acceleration = final velocity – initial velocity
change in time
A = 30 m/s – 0 m/s
10s
a = 30 m/s
a = 3 m/s/s or 3 m/s2

30. Practice Problem In 2.5 s a car increases its speed from
60 km/h to 65 km/h while a bicycle goes from rest to 5 km/h.
Which undergoes the greater acceleration?
What is the acceleration of each vehicle?

31. Answer : A = ending speed – initial speed time interval
Car’s acceleration:
a= 65 km/h – 60 km/h = 5 km/h = 2km/h/s
time interval s
Bicycle’s acceleration :
A = 5 km/h – 0 km/h = 5km/h = 2 km/h/s
2.5 s s

32. What is negative acceleration?
Also known as DECELERATION.
The negative rate of change of velocity.
Slowing down.
The amount of negative change of velocity in a time interval.
Ex:
10m/s – 25 m/s = - 15 m/s = - 3m/s/s or – 3m/s2
5 s s