Question

How does doubling speed of car effect stopping distance when the brakes are applied with same strength?

Answer 1

Let the stopping distance be s. We know from third equation of motion that s(distance) is directly proportional to u^2.
Thus, if the speed is doubled then then the stopping distance becomes 4 times the given value.

Answer 2

Initial speed=u;
Distance =s km
time= t sec
here final velocity=0 m/s
so, v²-u²=2as
-u²=-2as

so, we can see as, speed is doubled, the braking distance goes increases by 4 times . This is because the effect of velocity on Kinetic energy of car.