Question

I stopped the car by braking while driving.

Did most of the lost kinetic energy change to heat? If not, the energy change to a different form of potential energy?

Answer 1

When you stopped the car,most of its kinetic energy is converted to heat.When you applied the brake ,its pads exerted high pressure on the discs connected to shaft of the wheels.The strong normal force on the disc produced strong friction to oppose the motion.Other friction force was in between the wheels and the surface of the road.These frictions did negative work on the car to reduce its kinetic energy.

Yo can see sparking fire in between wheels and the road during applying strong brake on a moving vehicle in order to stop it. During sport bike or car stunts fire is produced from the tyres.This is done by applying strong front brake.