# 01Speed

Mo01TA of the Motion topic
• ## 01 Speed limitsMo01TAnugget01 Activity

What the activity is for

The purpose of this activity is to focus pupils' attention on the idea of speed, where it occurs in everyday life and what units it is measured in. You may also to start clearing up some difficulties:

• How average speed differs from instantaneous speed.
• The differences between the time shown on a clock and the time intervals used to calculate speeds.

What to prepare

• pictures of speed limit signs, speed cameras or a police speed trap
• stories of journeys, told in pictures, video clips, or words

What happens during this activity

Pupils use the visual stimuli to talk, in groups, about speed. Pupils will probably talk about speed in miles per hour (mph). This is fine for a starter activity. The police use a variety of methods to check the speed of moving vehicles. One technique is to time a vehicle as it moves between marks on the road. Painted white squares on roads provide police officers with markers. Bridges are also used as start and stop markers.

You could use it, with advantage, to explore the difference between time of day (o'clock) and time interval, or duration.

Teacher: When was she doing 40 mph?

Teacher: For how long was she getting farther away from the town?

It's also a natural place to start distinguishing between average and instantaneous speed, asking questions such as:

Teacher: How far did she go in that hour? What was her top speed?

Teacher: For how long did she keep it up?

• ## 02 Marble maniaMo01TAnugget02 Activity

### Fastest and shortest time

What the activity is for

The purpose of the activity is for pupils to recognise that speeds can be ranked by comparing times, provided that the distance travelled is the same. This being the case pupils should appreciate the fact that the shortest time means the greatest average speed.

What to prepare

• a simple race track – curtain rail, or the space between two metre rules
• marbles (or table tennis or polystyrene balls) and straws
• metre rules and stop clocks
• choose the materials to ensure that pupils are not timing unrealistically short events

What happens during this activity

Pupils blow the marble along the race track as quickly as possible. Pupils compete in groups of four. One pupil should blow the marble while the others record the time taken to complete a 200 centimetre course. The winner from each group enters the final stages of the competition.

Safety note: Be aware of pupils with significant asthma or breathing difficulties.

### Making and using measurements

In this activity it is not intended to have competitors racing against one another at the same time. Pupils can see the need to agree on reliable measurements to find the winner. The marble with the greatest average speed wins. Of course you don't need to know the speed. The shortest time wins. It is important in our context to extend the task to the calculation of average marble speed. Each group will therefore need to keep a record of their results. Depending on the age and ability of the pupils, you may provide a structured results table or encourage pupils to construct their own.

Some pupils will struggle with using the equation for speed. They might lack confidence with mathematics. You might want to try an approach which is based on simple proportions.

For example:

Teacher: The marble travelled 200 centimetre in 5 second – how many centimetres would it travel in 10 second? How many centimetres in 1 second?

Once pupils become familiar with the idea that speed is the distance travelled in 1 second, then solving problems by proportion can often become more straightforward.

Teacher: If I travel 60 metre in 10 second, how far will I travel in 1 second?

Mike: 60 metre divided by 10 second, so you travel 6 metre in 1 second.

Teacher: What is my speed?

Jaz: 6 metre every second, which is 6 metre / second.

For problems of this type, pupils are not directly using the equation for speed, they are calculating speed by proportion, knowing its units.

Part of the solution is also to do lots of examples using the equation – first on the board with the whole class suggesting the next step, then in small groups working on problems, and finally on an individual level. Some pupils may struggle with recalling the equation for calculating speed. By having the equation written large and displayed on the wall, you remove this hurdle. At this stage it is not necessary to engage in rearrangement of the equation to calculate distances. This will come later.

• ## 03 What speed?Mo01TAnugget03 Activity

### Calculating speed

What the activity is for

The purpose of this activity is for pupils to take measurements and to practise using the relationship:

speed = distanceduration

Although the distance travelled by each object and the time taken is different, pupils should appreciate that the calculated average speed allows the motions of different objects to be compared.

What to prepare

A circus of activities for measuring the average speed of different objects. Each circus station will need a metre rule and a stop clock and various objects which might include:

• moving clockwork, battery and friction-drive toys
• trolleys on an incline; bubbles rising in a water column; beads falling through a liquid column; paper helicopters

Aim for interesting moving objects, with a wide range of speeds.

What happens during this activity

In groups of two or three, pupils measure the time taken by different objects to travel different distances and use the relationship to calculate the average speed of each object.

At each station you might give instructions on what to do, what to measure and what to record. However it might be better to leave some space for group discussions on how best to carry out the measurements. By displaying the relationship beside each station you will reinforce the task in hand.

Pupils can then use calculated speeds to rank the objects in order of fastest to slowest, even though they did not travel for the same distance or length of time. A suitable end point might be to display results of measurements from each group. Is there a high level of agreement between the groups? If not, why not? Any ideas?

• ## 04 Along the roadMo01TAnugget04 Activity

### Measuring time travelled

What the activity is for

The purpose of this activity is for pupils to take measurements of time travelled (duration of travel) over a fixed distance and to practise using the equation:

speed = distanceduration

The context is provided by video clips of vehicles moving along a stretch of road.

What to prepare

• the video clip and a projector