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Rogue Physicist.  Free resources for physics education © 2006-2016 Dorian Pascoe.  Email: dorian.pascoe@hotmail.co.uk

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...calculating speed...

 

 

 

Objectives:

 

  
 

 

 

Miles per hour.

Not the only unit of speed.

 

Now that's a fast car!

  

 

• Know that speed can be measured in lots of different units, and be able to state a range of examples, including the S.I. units normally used for calculations at GCSE.

 

 

• Be able to use an equation to solve numerical problems involving speeds, distances and times.

 

 

• Be able to present calculations methodically and give the correct units with numerical answers.

 

  

 

 

 

 

 

Task 1 - Starter

 

  
 

 

Looking good!

 

 

Run!

 

 

 

 

 

  

 

Discuss with the person next to you:

 

 

1) What units can we can use to measure speed?

 

You will probably know several!

 

 

 

2) What does speed mean?

 

Try to come up with a sentence, without using any of the following words:

 

 

fast           slow           quick         rapid

 

  

 

 

 

 

 

Units of speed.

 
 

 

 

 

Units of distance can be combined with units of time to make units of speed.  Your teacher will explain how.

  
 

 

Units of distance

 

Units of time

 

Units of speed

 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

    

 

 

 

 

 

Task 2 - Which units should we use?

 

  
 

 

 

Go Turbo!

 

  

 

Complete the sentences by choosing an appropriate unit of speed for each of the things in the list.

 

 

The first one has been done for you!

 

 

Teacher note: there is a printable copy of this task here.

 

  

 

 

 

   

 

1) I would measure the speed of a car in units of miles per hour.

 

2) I would measure the speed of a snail moving in units of _________.

 

3) I would measure the speed of my fingernails growing in units of ________.

 

4) I would measure the speed of a planet orbiting the sun in units of _______.

 

5) I would measure the speed of a tectonic plate moving in units of ________.

 

6) I would measure the speed of a 100m runner in units of ____________.

 

 

 

 
 

 

 

Task 3 - Calculating speeds

 

  
 

 

Calculations!  Yeah!

 

 

  

 

Write the title Calculating Speed in your exercise book, and copy the definition below:

 

"The speed of an object is a measure of the distance travelled in a given unit of time.  Speed can be measured in lots of different units."

 

 

You will need a formula to solve numerical problems involving speeds, distances and times:

 

 

D = S × t

 

 

D = Distance, measured in metres (m)

S = speed, measured in metres per second (m/s)

t = time, measured in seconds (s)

 

Note: metres per second can be written as either m/s or ms-1.

  

 

 

 

 

 

 

Task 4 - Calculations

 

  
 

 

Think hard!

 

  

 

Your teacher will remind you how to use an equation triangle to rearrange the formula, and how to present a calculation by going through the first question on this sheet.

 

 

 

 

Complete the rest of the calculations in the same way, showing full working for all problems.

 

 

 

• Remember to convert units where necessary, before carrying out your calculation.

 

• Remember to give units with all numerical answers.

 

 

  

 

 

 

 

 

 

 

 

 

Task 5 - How fast are you moving right now?!

 

  
 

 

Think hard!

You may be moving faster than you think...

  

 

 

What speed are you moving right now, sat at your desk in the science laboratory?

 

 

 

 

Think about:

 

 

• ...the earth spinning...

 

• ...the earth orbiting the sun...

 

• ...the sun orbiting around the centre of the galaxy...!

 

 

 

 

 

Your teacher may explain the idea of Galilean reference frames.