Question

A car is being driven along a road at 25m/s when the driver suddenly notices that there is a fallen tree blocking the road 65m ahead. The driver immediately applies the brakes giving the car a constant velocity of 5m/s2. How far in front of the tree does the car come to rest?

Answer 1

Hi there!

We can use the following equation to solve for displacement:

vf² = vi² + 2ad, where:

vf = final velocity

vi = initial velocity

a = acceleration

d = displacement

Since the car will come to rest, vf = 0, so:

0 = vi² + 2ad

Plug in the given values:

0 = 25² + 2(-5)d (Breaking is a negative acceleration in this instance)

Solve:

0 = 25² - 10d

10d = 625

d = 62.5m

Subtract from the total distance from the car to the tree:

65 - 62.5 = 2.5m