Introduction to speed, velocity, and acceleration

1. Speed, Velocity &
Acceleration
Physics Fall 2025
Mr. Meeks

2. Motion
A. Movement – change in position
B. How do you know something moves? Motion
is a relative term
1. You can see it happening (observe)
2. Use a frame of reference
a. Sun, moon, stars
b. People standing beside the road
c. Cars moving down the highway

3. Distance vs. Displacement
A. Distance – length between two points
1. Use appropriate units…
a. Ex: Mississippi River
Appropriate – 3780 km
Inappropriate – 3,780,000,000,000 μm
(micro)
B. Displacement – length between two points and
the direction of motion (vector)
1. Ex: 5 miles north of Rock Rapids
2. Shortest length between points start and finish

4. 40 m
21 m S.E.

5. Speed
A. Definition - How fast something moves (rate
of change)
B. Requirements for speed
1. Distance traveled – 30 meters, 30 miles, 30
inches.
2. Time – how long it took to move a certain
distance. – 3hrs, 3 min, 3 ms.

6. Speed
C. Calculating speed
1. Formula = V = D/T
Speed = Distance V = Speed
Time D = Distance
T = Time

7. Speed
D. 3 Types of Speed
1. Instantaneous speed = speed at one moment
a. What is the instantaneous speed
according to the speedometer?
2. Constant Speed = speed that does not
change over a period of time.

8. Graph
a. Ex: setting the cruise
on a car at 55 mph.
b. Ex: What is the
constant speed of the car
in the following graph?
Car Ride to School
0
10
20
30
40
50
60
70
5
10
15
20
25
30
35
40
45
50
55
60
Time (Sec)
S
p
e
e
d
(m
p
h
)

9. 3. Average Speed
a. Definition – the total distance divided
by the total time.
b. Ex: A deer walked 5 m in 10 min, 8 m
in 23 min, and 7 m in 7 min. What was its
average speed?
5+8+7=20 meters
 10 + 23 + 7 = 40 min
 formula v = d/t
20 meters / 40 min
 .5 meters / min

10. Graph
Distance Time Graph
1. Definition – seeing the motion of an object over
time.
Water Aerobic Distance (meters)
0
200
400
600
800
1000
1200
1400
0 20 40 60 80
Time (min)
D
is
t
a
n
c
e
(
m
)

11. Practice
1. A car traveled 325 km in 4.5 hours. What was its average
speed in km/hr? What was its average speed in m/s?
2. A train speed along at 50 km/h for 8.25 hours. What was
its distance in km? What was its distance in meters?
3. How many hours would it take for a car to travel 450 km at a
rate of 35 km/hr?
72.2 km/hr 20 m/s
412.5 km 412,500m
12.9 hours

12. Speed vs. Velocity
A. Use same formula
 velocity = distance / time
B. Uses different labels
Speed – how fast something moves
1. Ex: a tornado is moving 15 mph.
Velocity – how fast something moves in a
certain direction.
1. Ex: a tornado is moving 15 mph to
the north.

13. Practice
1. 2 motorcycles traveling down the interstate in opposite
directions at 70 mph? Speed / Velocity?
2. 2 bikers traveling 70 mph along a path in the same
northern direction? Speed / Velocity?
3. 2 walkers walking down the road side by side at 5 mph?
Speed / Velocity?
4. What is the velocity of an object that travels 70 miles in
1.5 hours from Rock Rapids towards Sioux City?
Speed
Velocity
Speed
46.7 mph South

14. Practice
D. 1. What is the velocity of an airplane that is
traveling from Mexico to Canada. It traveled
1400 miles in 4.5 hours?
2. What is the velocity of a tornado that is
traveling from Omaha to Des Moines. It took
5.75 hours and traveled 200 miles?
311 mph North
34.8 mph East

15. Acceleration
A. Definition – rate of changing velocity
1. Ex: a dragster
 idle  green light  leaps forward
 faster  faster  drag chute  slower
 slower  stops.
2. Change of Velocity
a. Speed changes
b. Direction changes

16. Acceleration
B. Formula
1. Acceleration =
velocity(final) – velocity(initial)
time
2. *Always squared*
 m/s2
, mph2
, km/hr2
…

17. Example
1. A car’s velocity changes from 0 m/s to 30
m/s 10 seconds later. Calculate the car’s
average acceleration.
30 m/s - 0 m/s
10 sec
 3 m/s2

18. Practice
1. As a roller coaster starts down a hill, its speed
is 10 m/s. 3 seconds later, its speed is 32 m/s
at the bottom of the hill. What is the roller
coaster’s acceleration?
2. A bullet is fired from a gun. Its final velocity
is 750 m/s. It traveled this distance in 0.75
seconds. What is the bullets acceleration?