Physics Home Tutors in DHA Phase 1 Islamabad for O Level, A Level & FSc Students

Doubling speed does not double stopping distance — it roughly quadruples it when braking force is constant. That surprises many students until kinetic energy is brought into the picture.

The energy idea

Kinetic energy is ½mv². If speed doubles, v² becomes four times larger, so the car has about four times the energy to remove. Brakes do work over a distance; more energy means more distance (for the same average braking force).

Simple numbers

Suppose a car at 10 m/s needs about 5 m to stop under strong braking. At 20 m/s the kinetic energy is four times greater, so stopping distance is about 20 m under the same braking — not 10 m.

Reaction distance (how far you travel while deciding to brake) still grows linearly with speed, so total stopping distance grows even faster than the braking stretch alone.

Physics tutors in DHA Phase 1 Islamabad often use this example to connect equations of motion with everyday road safety.