# What effects how quickly a car stops?

## Presentation on theme: "What effects how quickly a car stops?"— Presentation transcript:

What effects how quickly a car stops?
Aims: To understand that stopping distances are related to friction and speed To understand what speed is and how it is measured To be able to interpret distance/time graphs

Speed and stopping Speed tells you how far you go in a certain time
The speed of a car affects how long it takes to stop The faster you are going, the longer it takes to stop Thinking time = the distance you travel whilst THINKING about stopping Braking distance = the distance you travel once you start to BRAKE

Stopping a car… Tiredness Too much alcohol Thinking distance
Too many drugs Poor visibility Wet roads Icy roads Braking distance Tyres/brakes worn out Driving too fast

Distance-time graphs 2) Horizontal line = 40 30 20 10
4) Diagonal line downwards = Distance (metres) 3) Steeper diagonal line = Time/s Diagonal line =

40 30 20 10 20 40 60 80 100 Distance (metres) Time/s
Distance (metres) Time/s How far had the object gone after 20 seconds? How far had the object gone after 60 seconds? When is the object standing still? When was the object travelling the fastest?

Activity 1 : Complete the worksheet (10 minutes)

Activity 2 How could we compare the speeds of a car on two different surfaces (The pink box on page 23 spotlight 8 may help)

d s x t Formula triangle for measuring speed Use this equation:
distance time s x t Speed is measured in many different units, e.g. m/s, km/h, km/s, miles per hour. The units of distance and time used will give the units to be used for speed.

Formula triangle

Cover the quantity you want to calculate - s (speed)
Examples A boy travels from his home to the cinema, a distance of 10 km in 1 hour. Calculate his speed in km/h. d (distance in km) Speed in km/h = t (time in h) d 10 km = 1 h s x t = 10 km/h Cover the quantity you want to calculate - s (speed)

Work out the speed of the two cars which is the fastest?

Complete the table on page 22 spotlight 8
then complete questions 1 to 5 on page 23.

How long did the journey take?
What was the total distance covered?  What was the average speed for the journey?  What was the average speed for the first 20 minutes and the last 20 minutes of the journey? Write a short story about this journey. What is happening in each 10 minute segment? (Finish for homework)