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Usain Bolt blitzed the field once again in the
100m sprint at the Rio Olympics, making it
three gold medals in a row in the event.
So how fast can he run?
And how does that top speed compare?
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Bolt in the 2016 Rio Olympics
Bolt's winning time of 9.81 secs equates to
an average speed of 36.7 kmh. However, that's
just an average - his actual top speed is much
faster than that. In 2009 when he set a new
world record of 9.58sec, it was calculated that
Bolt's speed peaked at 12.27 meters per second
or 44.16 kmh. (1 km = .6miles)
 A 5K race is 3.1 miles
 To put that in perspective, someone out for a jog
travelling at the reasonable pace of 14kmh, will
cover just 38m in the time it took Bolt to win his
gold medal.
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Lindsey Vonn – best downhill skier
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If you want to be the fastest in the world –
you have to understand some basic (and not
so basic) physics!
Let’s start by adding to our understanding of
how things move
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Acceleration is a change in velocity by
 Changing speed:
▪ Starting
▪ Stopping
▪ Speeding up
▪ Slowing down
 Or changing direction
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Acceleration can be positive or negative
 Speeding Up – Positive acceleration (+)
 Slowing Down – Negative acceleration (-)
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Units – measured in m/s2
Acceleration is caused by unbalanced forces
Calculating Acceleration:
Acceleration = change in
velocity that occurs over
a certain amount of time
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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
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Units: Measured in m/s
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Acceleration is a change in direction and/or
speed, not just limited to “speeding up”
(which is how most people misuse the term).
It can also mean to slow down or change
direction.
Write
this in
your
notes!
Speed is calculated by dividing distance by
time.
Remember – average speed is speed
over a given amount of time! So the
formula is:
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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 = 5m/s
Remember to
include the
UNITS!!
Velocity = Final Distance – Initial Distance
Final Time – Initial Time
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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. A vector means size and direction.
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There must be direction.
 Speed = 3 m/s
 Velocity = 3 m/s, heading northeast
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Speed describes distance and time
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Velocity describes distance, time, and
direction
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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.
How are they connected?
Acceleration is a change in speed, direction or
BOTH!
 Acceleration is simply the measure of the
change in velocity. It occurs when there is a
change in speed, direction, or both.
 If you kick a soccer ball down the field during a
game, the direction of the ball and the speed at
which it travels is constantly changing. This
means that the acceleration of the ball is
continuous as well.
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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
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Now that you have filled in the blanks with
either “speed” or “velocity”. Go back to the
sentences that are examples of velocity.
Highlight or underline the key words that
make them examples of velocity.
Hint: look for directional words!
To get full credit for each problem, you need
to show the first step which is to put the
distance (with units) over the time traveled
(with units).
 The show the answer WITH units!!
1. 600 miles – distance, 3 hours is time.
If S = d/t then the problem is:
S = 600 mi
3 hrs = 200 mi/hr or mph
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Get your science journal now.