3-Spr1-B

Outcomes

• Pupils can identify factors which affect reaction time
• Pupils can appreciate that stopping distance is a combination of thinking distance and stopping distance
• Pupils can list factors which affect thinking distance (the person) and braking distance (the vehicle)

Specification References

1.17 describe the factors affecting vehicle stopping distance including speed, mass, road condition and reaction time

Starter

Put the following question on the board for the pupils to read as they come in:

"In 1991 Leoroy Burrell and Carl Lewis took part in a 100m sprint in Ney York. Burrell ran the 100m course in 9.783s whilst Lewis took only 9.764s. However, it was Burrell who took home the gold and Lewis the silver? How could this be fair?"

The answer is down to reaction time. Burrell's reaction time was only 117ms whereas Lewis took 166ms. This meant that Burrell got to the finish line first despite running the course slower.

Main Body of Lesson

Ruler dropping - In pairs pupils take it in turns to drop a ruler from just abover their partners fingers. The catching partner attempts to catch the ruler as quickly as possible. This is repeated 5 times and an average taken.

Using <math>\sqrt{s/2g}</math> where s is the distance fallen and <math> g = 9.81m/s^2 </math> to give an approximate reaction time.

Next have them repeat the test with the catcher counting down from 1000 or going through the alphabet backwards to add a distraction. This should increase their reaction time. This is where you can introduce the concept of thinking time when considering stopping distance.

There are lots of computer based reaction timers (dot, BBC sheep and traffic light). These can be done on the whiteboard or can be given to the pupils to tackle as part of their homework. They could test themselves and others in thier families and then try retesting them with distractions.

The highway code has a section on stopping distance (the 2 second rule, you could do the math on this if you wish). They also publish average stopping distance data. This can be plotted on one set of speed vs. distance axes. Have the pupils plot 3 lines and extrapolate data from the graph - This could be set as homework. There is a sheet about this in the folder

There is another website which runs simulations of people driving at different speeds and looks at whether you'd drive into a pedestrian. Here's the link. The more cynical amonst you might notice that the goal posts get moved slightly to illustrate their point (try comparing 20mph + drink driving with 30mph sober in 2 different windows).

Plenary

Can talk about how improtant reaction times are in the 100m sprint. Here is a useful website with some good facts on.

Additional Information

Notes

The wikipedia page on mental chronometry is very good, especially the types of tests available. Average response time for simple visual stimuli is 190ms