Speed D. Crowley, 2007

Speed  To be able to calculate speed, and to be able to predict how the forces acting upon an object will affect the speed

Question  Some year sevens ran to the end of the field  How fast were they running?  What extra information would you need to answer this question?  Some year sevens ran to the end of the field  How fast were they running?  What extra information would you need to answer this question?

What is Speed?  What is speed?  What is it measured in?  How can we work out someone’s speed?  You have five minutes to discuss with your partner the above questions…  What is speed?  What is it measured in?  How can we work out someone’s speed?  You have five minutes to discuss with your partner the above questions…

Speed  Speed is a measurement of how quickly something is travelling at, which can be in m/s; km/h; mph; cm/year etc…  To work out the speed of something, you need to know the distance covered and the time it took to get there  So speed = distance / time  E.g. 30mph = 30 miles traveled in 1 hour  E.g. 10m/s = 10 meters traveled in 1 second  E.g. 1cm/year = 1 centimeter traveled in 1 year  Speed is a measurement of how quickly something is travelling at, which can be in m/s; km/h; mph; cm/year etc…  To work out the speed of something, you need to know the distance covered and the time it took to get there  So speed = distance / time  E.g. 30mph = 30 miles traveled in 1 hour  E.g. 10m/s = 10 meters traveled in 1 second  E.g. 1cm/year = 1 centimeter traveled in 1 year

Speed Formula Speed (s) Distance (d) Time (t)

Examples  Jack ran 100m in 12 seconds. What speed was he traveling at?  Jack then ran 100m again, but this time it was much more windy, and it took him 15 seconds. What was his new speed, and why was this different?  My car was going at 50mph for 1 hour. How many miles did I travel  My car was going at 50mph, and I traveled 20 miles. How long did this take me?  Jack ran 100m in 12 seconds. What speed was he traveling at?  Jack then ran 100m again, but this time it was much more windy, and it took him 15 seconds. What was his new speed, and why was this different?  My car was going at 50mph for 1 hour. How many miles did I travel  My car was going at 50mph, and I traveled 20 miles. How long did this take me? Speed Distance Time

Examples  Jack ran 100m in 12 seconds. What speed was he traveling at? Speed = 100 / 12 = 8.34m/s  Jack then ran 100m again, but this time it was much more windy, and it took him 15 seconds. What was his new speed, and why was this different? Speed = 100 / 15 = 6.67m/s (more air resistance)  My car was going at 50mph for 1 hour. How many miles did I travel Distance = 50 x 1 = 50mph  My car was going at 50mph, and I traveled 20 miles. How long did this take me? Time = 20 / 50 = 0.4 hours (24 minutes)  Jack ran 100m in 12 seconds. What speed was he traveling at? Speed = 100 / 12 = 8.34m/s  Jack then ran 100m again, but this time it was much more windy, and it took him 15 seconds. What was his new speed, and why was this different? Speed = 100 / 15 = 6.67m/s (more air resistance)  My car was going at 50mph for 1 hour. How many miles did I travel Distance = 50 x 1 = 50mph  My car was going at 50mph, and I traveled 20 miles. How long did this take me? Time = 20 / 50 = 0.4 hours (24 minutes) Speed Distance Time

Forces & Speed  How do forces affect speed?  What happens when you travel very quickly (i.e. on a motorway in the car)  What is it so much effort for a rocket to take off into space?  Why is it more fun to be going downhill on your bike, rather than uphill?!  How do forces affect speed?  What happens when you travel very quickly (i.e. on a motorway in the car)  What is it so much effort for a rocket to take off into space?  Why is it more fun to be going downhill on your bike, rather than uphill?!

Forces & Speed  Forces can affect speed, both positively and negatively  Forces can help move objects, i.e. a car engine delivers a force to turn the wheels of a car, moving it  For example, cycling downhill is easier than uphill as gravity is helping pull you down  Forces can affect speed, both positively and negatively  Forces can help move objects, i.e. a car engine delivers a force to turn the wheels of a car, moving it  For example, cycling downhill is easier than uphill as gravity is helping pull you down Bike 1 traveling steadily at 10mph - engine is working against slight air resistance Bike 2 traveling steadily at 100mph - engine is working very hard against large air resistance

Forces & Speed  The opposite is true of space rockets, which must fight gravity to escape the Earth  As you go very quickly you also experience more friction (increased air resistance, which causes you to slow down)  Different surfaces also have more / less friction - think about what is easier to run on, carpet or ice?  The opposite is true of space rockets, which must fight gravity to escape the Earth  As you go very quickly you also experience more friction (increased air resistance, which causes you to slow down)  Different surfaces also have more / less friction - think about what is easier to run on, carpet or ice? Bike 1 traveling steadily at 10mph - engine is working against slight air resistance Bike 2 traveling steadily at 100mph - engine is working very hard against large air resistance

Experiment  How does road surface affect speed?  Next lesson you are going to investigate this…  It is up to you and a partner to plan an investigation to answer this question  The equipment you will be able to use includes: strips of sandpaper; carpet; ramps; string; Newton meter (measure force); marble; ruler; stop-clock  How does road surface affect speed?  Next lesson you are going to investigate this…  It is up to you and a partner to plan an investigation to answer this question  The equipment you will be able to use includes: strips of sandpaper; carpet; ramps; string; Newton meter (measure force); marble; ruler; stop-clock