
Acceleration is a change in velocity by
 Changing speed:
▪ Starting
▪ Stopping
▪ Speeding up
▪ Slowing down
 Or changing direction

Acceleration can be positive or negative
 Speeding Up – Positive acceleration (+)
 Slowing Down – Negative acceleration (-)

Units – measured in m/s2

Acceleration is caused by unbalanced forces

Calculating Acceleration:
Final Speed – Initial Speed
Time

A way to describe motion.
 Average speed - Rate of motion calculated by
dividing the distance traveled by the amount of time
it takes to travel that distance
 Constant speed - Speed that does not change
 Instantaneous speed - Speed of an object at any
given time

Units: Measured in m/s
Speed is calculated by dividing
distance by time.
Distance
Speed =
Time
Divide Distance by Time
Distance ÷ Time = Speed
Speed = Distance ÷ Time
Multiply Speed and Time
Distance = Speed X Time
Speed X Time = Distance
Divide Distance by Time
Distance ÷ Speed = Time
Time = Distance ÷ Speed

A football field is about 100 m long.
If it takes a person 20 seconds to run
its length, how fast was the football
player running?
A football field is about 100 m long. If it takes a
person 20 seconds to run its length, how fast
was the football player running?
Speed = Distance ÷ Time
Speed = 100 m ÷ 20 s
Speed = 5 m/s
Remember to
include the
UNITS!!
Velocity = Final Distance – Initial Distance
Final Time – Initial Time

Velocity is speed with direction

Calculating velocity is the same as calculating
speed (distance/time).
 The difference is that velocity is what physicists
call a vector.

There must be direction.
 Speed = 3 m/s
 Velocity = 3 m/s, heading northeast

Speed describes distance and time

Velocity describes distance, time, and
direction

You can say the top speed of an airplane is
300 kilometers per hour (kph). But its
velocity is 300 kph in a northeast direction.
Which of the following sentences contain an example of
velocity and which contain an example of speed?
A.
Five seconds into the launch, the rocket was shooting
upward at 5000 meters per second.Velocity
B.
Cheetahs can run at 70 miles per hour. Speed
C.
Moving at five kilometers per hour, it will take us eight
hours to get to the base camp. Speed
D.
The car covered 500 kilometers in the first 10 hours of its
northward journey. Velocity
E.
Roger Bannister was the first person to run one mile in less
than four minutes. Speed

Podcast
Speed
Velocity
m/s
Time
Distance
m/s2
Acceleration
Direction
m/s north
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Time
m/s
m/s north
m/s2
Distance
Direction