Video Transcript
The thinking distance and braking
distance of a car at different initial speeds are shown in the graph. The thinking distance is in blue
and the braking distance is in orange. How much greater is the braking
distance than the thinking distance when the initial speed is 90 kilometers per
hour?
In this question, we are shown a
graph that plots the thinking distance and braking distance for a car at different
initial speeds. We want to find the braking
distance and thinking distance for this car when it has an initial speed of 90
kilometers per hour and determine how much greater the braking distance is than the
thinking distance.
On this graph, let’s mark the point
on the 𝑥-axis that corresponds to an initial speed of 90 kilometers per hour. Now let’s draw a dashed vertical
line from 90 kilometers per hour up to the blue and orange lines. Remember that the thinking distance
is shown in blue and the braking distance is shown in orange. If we now draw a dashed horizontal
line from the orange line to the 𝑦-axis, we will be able to find out the braking
distance of the car by reading the value off the 𝑦-axis. After drawing this dashed
horizontal line, we see that the braking distance for the car with an initial speed
of 90 kilometers per hour is 45 meters.
Now let’s work out the thinking
distance. If we draw a dashed horizontal line
from the blue line to the 𝑦-axis, we can read off a value of 37 meters for the
thinking distance of the car when it has an initial speed of 90 kilometers per
hour.
We want to calculate how much
greater the braking distance is than the thinking distance when the initial speed is
90 kilometers per hour. So we simply need to do the
calculation braking distance minus thinking distance. Substituting the values of braking
distance and thinking distance into this equation, we find that the difference
between the two is equal to 45 meters minus 37 meters, which is equal to eight
meters.
Thus, we have arrived at the
correct answer. The braking distance is eight
meters greater than the thinking distance when the car’s initial speed is 90
kilometers per hour.
