MOVEMENT AND CHANGE Stopping Distances

Lesson Aims Consolidate understanding of how to interpret speed-time graphs. Understand what makes up the “stopping distance” of a vehicle. Know the factors that affect stopping distances

HOMEWORK Make sure your homework booklet is inside your exercise book. If you have not stuck it in your book write your name on it!

Speed Time Graphs To show your understanding of this topic: Answer question number 1 & 2 off page 131 of Physics text book It should take you about 13 minutes to do this including the time taken to draw a graph

Stopping distance

Stopping distances Accidents on motorways often involve vehicles of great mass travelling at large speeds. The forces involved when these vehicles suddenly stop are enormous.

Stopping distances Compare the following vehicles. A car travelling at 25 m/s An identical car travelling at 35 m /s A coach travelling at 20 m / s Which will be the hardest to stop? Which will need the largest force to stop?

Stopping safety SpeedThinking distance Braking distance Overall stopping distance 30 mph30 ft45 ft75 ft 50 mph50 ft125 ft175 ft 70 mph70 ft245 ft315 ft

Stopping safety Thinking distance There is always a short time between our eyes seeing that something has to be done and our brains actually moving our muscles. This time is called the “reaction time”

For a healthy person this is usually about half a second (it is less for younger people and longer for older people). The “thinking distance” is how long a car will travel during a drivers reaction time. The faster a car is travelling, the greater the thinking distance.

Stopping distances What factors do you think determine how long it takes a car to stop? The mass of the vehicle The speed of the vehicle The driver’s reaction time

Stopping distances The greater the mass of a vehicle, the longer it’s stopping distance. The greater the speed of the vehicle, the longer it’s stopping distance. The longer the driver’s reaction time, the longer its stopping distance

Question time! Your teacher will now give you a sheet with some information and questions on. Stick this sheet in your exercise books and answer the questions. This task should be completed as part of your next homework.