# Braking Distance

Here is some braking-distance
data.

You might want to compare the following solution with the

##

A Solution:

The kinetic energy of the truck
is given by:

so if you double the speed
of the truck, you give it **4 times the kinetic energy**.

According to the work-energy
equation:

(Work done by the net
force equals the change in the object's kinetic energy) in order
to stop the truck when it is going twice as fast, the brakes of the
truck must do** 4 times the work** as before.

If the force exerted by the brakes is more-or-less constant,
then:

work done by the brakes
= -(force)(distance).

Assuming that the brakes can exert the same maximum force
regardless of the speed of the truck (which is reasonable), the
braking distance must be **4 times** as
much (48 meters) if the speed is doubled.

last update May 21, 1999 by JL
Stanbrough