1. Speed and Velocity What is speed, velocity and acceleration?
How does speed, velocity and acceleration relate
to Forces & Motion?

2. How does MOTION relate to POSITION and TIME?
MOTION often includes speed and is a change in position.
SPEED then is the rate of change in position or the “rate of motion.”
QUESTION: Do you have to see something move to know that motion has taken place?
ANSWER: No – because the only thing needed is a reference point to see that something has changed position.

3. Measures of Speed
Pretend you are looking at your car's speedometer while you are driving. The reading you get from your speedometer is…
instantaneous speed.
This is the speed that you are traveling at that moment.

4. Now, let’s say you are on a highway, a car may travel at the same speed for a long period of time this would be…
constant speed.
This is the speed that does not vary – cruise control.

5. Now, let’s say that you are trying to determine the distance you are going to traveled in a given amount of time– this would be…
Katy
Houston
average speed.
Speed is the distance traveled per unit of time.

6. Distance, Speed and Time is shown in the equation:
Calculating Speed
Distance, Speed and Time is shown in the equation:
speed =
distance
time
...or shortened:
s = d t
s = Speed d = Distance t = Time

7. Manipulating the Equation
The equation reads -
but it can be rearranged to solve for any variable.
s = d t
So, to find DISTANCE, we need to MULTIPLY speed and time.
d = s x t
divide D
meters
And, to find TIME, we need to DIVIDE distance by the speed.
t = d s S
m/s T
seconds
multiply

8. FIVE Step Approach to Solving Problems
(G )Step 1 Read the problem. Write down the GIVENS
(U) Step 2 Write down the UNKNOWNS.
What you are looking for?????
(E) Step 3 Write down the EQUATION.
(S) Step 4 SUBSTITUTE the numbers.
(S) Step 5 SOLUTION. Box Answer with UNITS!

9. “A car traveled 110 miles in 2 hours.”
Consider the problem…
“A car traveled 110 miles in 2 hours.”
Step 1 Read the problem. Write down the GIVENS.
110 miles
2 hours
Formula
Substitute
Answer
Units, units, units!
d =
t =
s =

10. ? “A car traveled 110 miles in 2 hours.” 110 miles 2 hours Formula
Step 2 Write down the UNKNOWNS. What are you trying to find?
Formula
Substitute
Answer
Units, units, units!
d =
110 miles
t =
2 hours
s = ?

11. ? “A car traveled 110 miles in 2 hours.” s = d t Formula Substitute
Step 3 Write down the EQUATION.
s = d t
Formula
Substitute
Answer
d =
110 miles
t =
2 hours
s = d t
s = ?
Units, units, units!

12. “A car traveled 110 miles in 2 hours.”
Step 4 Substitute the numbers. Step 5 SOLUTION. Box Answer with Units.
2 hours
110 miles
Formula
Substitute
Answer d t
S =
d =
110 mi
110 mi
2 hr
S = 55
mi/hr
S =
2 hours
t =
s = 55
mi/hr
Units, units, units!

13. Do the problems
1-3 on your notes.

14. Consider the problem…
“A runner’s average speed during the 10 kilometer race was 20 km/hr. What was his time?’”
Step 1 Read the problem. Write down the GIVENS.
Speed of runner: 20 km/hr
10 km
Formula
Substitute
Answer
d =
t =
s =
Units, units, units!

15. “A runner’s average speed during the 10 kilometer race was 20 km/hr
“A runner’s average speed during the 10 kilometer race was 20 km/hr. What was his time?’”
Step 2 Write down the UNKNOWNS. What are you trying to find?
Speed of runner: 20 km/hr
10 km
10 km
Formula
Substitute
Answer
d =
t = ?
s =
20 km/hr
Units, units, units!

16. “A runner’s average speed during the 10 kilometer race was 20 km/hr
“A runner’s average speed during the 10 kilometer race was 20 km/hr. What was his time?’”
Step 3 Set up the EQUATION.
Speed of runner: 20 km/hr
10 km
Formula
Substitute
Answer
d =
10 km
t = d s
t = ?
s =
20 km/hr
Units, units, units!

17. “A runner’s average speed during the 10 kilometer race was 20 km/hr
“A runner’s average speed during the 10 kilometer race was 20 km/hr. What was his time?’”
Step 4 SUBSTITUTE the numbers. Step 5 SOLUTION. Box Answer with Units.
Formula
Substitute
Answer
d =
10 km
0.5 hr d
t = s
t =
t =
10 km
20 km/hr
0.5 hr
s =
20 km/hr
If the runner’s average speed was 20 km/hr during the 10km race, the runner’s time was 0.5 hours.
Units, units, units!

18. Do the problems
4-5 on your notes.

19. “You decide to go to Dallas to visit your friends
“You decide to go to Dallas to visit your 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 Read the problem. Write down the GIVENS.
Step 3 Set up the EQUATION.
Step 4 SUBSTITUTE the numbers. Step 5 SOLUTION. Box Answer
with units.
Step 2 Write down the UNKNOWN. What are you trying to find?
Formula
Substitute
Answer
d =
280 mi
4 hr
t =
d = s x t
d = 70mi/hr x 4 hr
d = 280 miles
s =
70 mi/hr
Units, units, units!
If I drive 4 hours at 40mph, the distance from Houston to Dallas is 280 miles.

20. Do problem 6 on your notes.

21. A distance/time graph makes it possible to “see” speed.
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 in your notes & answer the questions.

23. (Reading on your speedometer)
Instantaneous speed-
at that moment
Average speed-is over time

24. What is the difference between speed and velocity?
55 mi/hr
Speed is how fast
Velocity has speed & direction.
55 mi/hr
All of these cars had the same SPEED but,
different VELOCITIES because they were traveling in different directions.
If you change direction, you have changed your velocity – and if you have changed your speed, you have changed your velocity. Therefore, any
change in speed OR direction is a
change in velocity!
55 mi/hr

25. Why is it important to know the
VELOCITY of a tornado?

26. Acceleration … is defined as the change in velocity over time.
final velocity – initial velocity
time
acceleration =
Vf - Vi t
a =

27. Types of Acceleration Positive Acceleration Negative Acceleration
Velocity and acceleration are in the same direction.
Object SPEEDS up.
Negative Acceleration
Velocity and acceleration are in opposite
direction.
Object SLOWS down.

28. A go-cart started from the top of a hill at 5 meters per second
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 Read the problem. Write down the GIVENS.
5 m/s
top
Formula
Substitute
Answer
Vf =
Vi=
t =
a =
In 6 s
bottom
35 m/s

29. A go-cart started from the top of a hill at 5 meters per second
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 Write down the UNKNOWNS. What are you trying to find?
5 m/s
top
Vf =
35 m/s
6 s
Formula
Substitute
Answer
Vi=
5 m/s
t =
6 s
a = ?
bottom
Finish:
final Velocity
35 m/s

30. A go-cart started from the top of a hill at 5 meters per second
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?
Initial Velocity
Step 3 Set up the EQUATION.
5 m/s
top
Vf - Vi t
Vf =
35 m/s
Formula
Substitute
Answer
6 s
Vi=
5 m/s
Vf - Vi t
t =
6 s
a = ?
bottom
35 m/s
Final Velocity

31. Step 4 SUBSTITUTE the numbers. Step 5 SOLUTION. Box Answer with Units.
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 SUBSTITUTE the numbers. Step 5 SOLUTION. Box Answer with Units.
Vf =
35 m/s
Formula
Substitute
Answer
Vf - Vi t
Vi=
5 m/s
35m/s – 5 m/s 6s
30 m/s
6 s =
5 m/s2
t =
6 s
a =
5 m/s2
The go-cart that traveled from 5m/s to 35 m/s in 6 seconds had an acceleration of 5m/s2.

32. Do the problems
7-9 on your notes.