**Speed**

Starter

What measures do we use these units for?

(a) miles

(b) hours

(c) miles per hour

What does this tell you about your answer for (c) compared to the answer for (a) and (b).

Calculations with Speed

A car drives 375 miles in a time of 15 hours. Work out the average speed. Give the units of your answer.

A cyclist cycles 24 miles at an average speed of 8 miles per hour. Work out the time taken.

Compound units

Speed is a compound measure - it is calculated from simpler measures.

**L.O. - Calculate with speed**

Starter

What measures do we use these units for?

(a) miles

= distance

(b) hours

= time

(c) miles per hour

= speed

What does this tell you about your answer for (c) compared to the answer for (a) and (b).

That speed depends on distance and time

The unit of speed can tell you how it is calculated for example a speed in

miles per hour was calculated by dividing a distance in miles by a time in hours.

A unit of metres per second means a distance in metres was divided by a time in seconds.

Calculations with Speed

A car drives 375 miles in a time of 15 hours. Work out the average speed. Give the units of your answer.

375/15 = 25 miles per hour

A cyclist cycles 24 miles at an average speed of 8 miles per hour. Work out the time taken. Give the units of your answer.

24/? = 8 24/8 = 3 hours

Main Activity 1

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Main Activity 1 Answers

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(a) 4 kilometres per hour (b) 47 miles per hour

(c) 6 metres per second (d) 54 miles per hour

(a) 125 kilometres (b) 120 miles

(c) 120 metres (d) 96 kilometres

(a) 5 hours (b) 4 seconds

(c) 7 hours (d) 5 seconds

Calculations with Speed

A car drives 375 miles in a time of 12 hours 30 minutes. Work out the average speed. Give the units of your answer.

A cyclist cycles 24 miles at an average speed of 5 miles per hour. Work out the time taken. Give your answer in hours and minutes.

Calculations with Speed

A car drives 375 miles in a time of 12 hours 30 minutes. Work out the average speed. Give the units of your answer.

12 hours 30 minutes = 12.5 hours.

375/12.5 = 30 miles per hour

A cyclist cycles 24 miles at an average speed of 5 miles per hour. Work out the time taken. Give your answer in hours and minutes.

24/5 = 4.8 hours

4.8 hours = 4 hours 48 minutes

Main Activity 2

Answer the questions on the speed, distance and time calculations sheet.

1) 120 km/h

2) 70 mph

3) 12 km/h

4) 900 metres

5) 16 km

6) 315 km

7) 2 hours 30 minutes

8) 1 hour 15 minutes

9) 1 hour 20 minutes

**Key**

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