Calculating Speed

1. Calculating Speed

2. Daily Science
• Write down the following words in your note
section:
• Motion, reference point, acceleration, velocity
• With your groups discuss what each word
means to you. Come up with a general idea
and everybody needs to write it down
• Then answer the following question:
• How do you know an object is in motion?

3. Motion
• For an object to be in motion you must use a
reference point
• A reference point is a stationary place or
object used for comparison to determine if
something is in motion.
• An object is in motion if it changes position
relative to a reference point.

4. Calculating Speed
Two things are needed to calculate speed:
1. Distance the object travels.
Units that are included: (meter (m), centimeter (cm),
kilometer (km), feet (ft.))
2. The time it takes the object to travel that distance.
Units that are included: (seconds (s), minutes (min.),
hours (h))

5. Calculating Speed
When you know the distance and time of the
object you need to use the following equation.
Speed = Distance/ Time or S=d/t
For example:
An object that travels a distance of 10 meters in 2
seconds you would do this:

6. Calculating Speed
Since you know the distance and time you just put the
numbers in the correct variables:
d= 10 meters
t= 2 seconds
Therefore you can find the speed:
s= 10m/2 sec.
s= 5m/s
Always include the unit for distance and time in your
answer (m/s).

7. Calculating Speed
To find the average speed of an object is similar to
finding the average of a group of things:
All you need to do is add up all of the distances together
and all the total time together and use the same
equation.
For example:
A biker travels 32 km in 2 hours during the first leg of the
race and on the second leg of the race he traveled 13 km
in 1 hours.

8. Calculating Speed
Since we know the distance and time we can find the average speed
of the biker:
The two distances that he traveled was 32 km and 13 km
The two times he traveled that in was 1 hour and 2 hours
Add the distances together:
d= 32 km + 13 km = 45 km
t= 2 hour + 1 hour = 3 hours
s= 45 km/3 hours
s= 15 km/hr

9. Calculating Speed
Speed doesn't tell us everything about the motion
of an object.
To fully understand motion you also need to know
the velocity of an object.
When you know the speed and direction of an
object you know the velocity

10. Other Equations to Know
Speed= distance/time
Distance= Speed x Time
Time= Distance/Speed

11. Practice Problems
1. A car traveled 15 hours to travel a distance of 653 km.
How fast was this car driving?
2. A person walked for 35 seconds with a speed of 1.5
m/s . How far did they walk?
3. A truck drove for 320 km at a speed of 35 km/h. How
long did it take them?