8.6B - differentiate between speed, velocity, and acceleration6.8C – calculate average speed using distance and time measurements

Students will be able to:

Define speed Calculate speed Distinguish between instantaneous,

constant and average speed

When it comes to movement, human beings are fascinated by speed.

From vintage muscle cars to turbo-powered sports cars, we love things that go fast.

We even have track and field competitions and the Olympic Games that celebrate those humans that can move most quickly.

Think for just a second – what do you think of when you hear the word “fast”?

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?

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) – he ran 27.3 mph!

Lindsey Vonn – best downhill skier

Is a way to describe motion. Speed is a type of rate. A rate tells you the

amount of something that occurs during a given unit of time.

If you know the distance an object travels in a certain amount of time, you know the speed of the object.

▪ Speed is captured in a variety of contexts. What this means is that although the formula for calculating speed doesn’t change, what the numbers mean does change.

▪ 3 “types” to be aware of:

▪ Instantaneous speed

▪ Constant speed

▪ Average speed

Instantaneous Speed- The speed of an object can change as it moves. 'Instantaneous' comes from the word 'instant'

meaning only one specific moment. The instantaneous speed is the speed of an object

at a certain instant of time.

Speed at one instant = instantaneous speed

Speed over a period of time = average speed

One Minute

Constant Speed -

If the speed of an object does not change during its motion, the object is traveling at a constant speed

Constant speed – speed of an object that does not change

Examples:

▪ cars on cruise control

▪ Satellite traveling above earth

Average Speed – Most objects do not move at a constant speed

very long. Most moving objects change speed many times

while in motion. The marathon runners cannot run at a constant

speed during the entire race.

At the starting line, there are many runners crowded together, so the runners are forced to move slowly.

As the crowd thins out, a runner can increase his or her speed. The runner may slow down as he or she climbs a hill and

increases speed going down the hill. When the race is over, a runner may calculate his or her

average speed.

Average speed - Rate of motion calculated by dividing the total distance traveled by the total amount of time it takes to travel that distance – it includes all of the starts, stops and changes in speed over that time period.

Speed is calculated by dividing distance by time.

Remember – average speed is speed over a given amount of time! So the formula is:

Scientific Units: Measured in m/s or km/h

Distance measurement/timeunits

(the given distance/time)

English Units: Mph (miles per

hour) Foot/sec Boats use knots (kn)

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 sSpeed = 5 m/s

Remember to include the

UNITS!!

A swimmer can swim 1000 m in 360 seconds. What is her average speed in m/s?

A swimmer can swim 1000 m in 360 seconds. What is her average speed in m/s?

Speed = d/t So Speed = 1000 m/ 360 sec S = 2.78 m/s

And you will need to get a few supplies –you are responsible for keeping up with the supplies and for bringing them back in.

Brain Pop Crash Course