5.6 Stopping Distances

The graphs in Figure 1 show how the velocity of two cars, A and B, change from the moment the car drivers see an obstacle blocking the road.

Figure 1

Using Figure 1, state and explain which car has a smaller stopping distance.

One of the car drivers was on their phone. The other driver is wide awake and alert.

Determine which driver drove which car.

A different driver in car C has a stopping distance of 15 m and a thinking distance of 4 m.

Calculate the braking distance of the driver in car C.

Table 1 shows the reaction times of three people driving under different conditions.

Table 1

Figure 1 show how the thinking distance for the three drivers, A, B and C, depends on how fast they are driving the car.

Figure 1

Match each graph line in Figure 1 to the correct driver by writing A, B or C in the box next to the correct line.

Give two reasons not mentioned in Table 1 as to why driver A would have the longest reaction time.

Driver B travels at 10 m/s.

Use Figure 1 to determine the thinking distance of driver B. Clearly show your working on the graph.

Driver B has a braking distance of 6 m.

Calculate the stopping distance for driver B.

An investigation was carried out to show how thinking distance, braking distance and stopping distance are affected by the speed of a car.

The results are shown in Table 1 below.

Table 1

Complete Table 1 by adding in the missing values.

Figure 1 shows the stopping distance for a family car, in good condition, driven at 20 m/s on a dry road. The stopping distance has two parts.

Figure 1

Complete Figure 1 by adding an appropriate label to the first part of the stopping distance and state one factor that changes both the first part and the second part of the stopping distance.

Write down the equation relating braking distance, thinking distance and stopping distance. 

Midway through a long journey, a lorry driver is travelling along a road at 25 m/s when she spots red traffic lights 200 m ahead.

The lorry driver usually has a reaction time of 0.84 s but she is tired so her reaction time is twice as long. 

Calculate the lorry driver's thinking distance.

Figure 1 is a graph showing braking distances for the average lorry at different speeds in kilometres per hour (km/h).

25 m/s is equal to 90 km/h. The lorry's brakes can produce a deceleration of 3.5 m/s².

Estimate the stopping distance of the lorry at this speed.

Give your answer to 2 significant figures.   

In reality, the lorry comes to a stop only 5 m before the red light, even with brakes being fully applied. 

Suggest two reasons why this may have happened.