The thinking distance depends on the reaction time of the driver which could be affected by drugs, alcohol, distractions and tiredness. A faster speed increases both thinking and braking distance, increasing the total stopping distance.

An object with less speed and more mass could potentially have the same Kinetic energy. The equation for Kinetic Energy is: KE = 1/2 mv2. Kinetic energy has a direct relationship with mass, meaning that as mass increases so does the Kinetic Energy of an object. However, mass and velocity are indirectly related.

Your braking distance will quadruple when your speed doubles because the work that it takes to stop your car means removing all of the kinetic energy. That means that for a fixed maximum braking force, your braking distance will be proportional to the square root of the velocity.

However, the braking distance increases by a factor of four each time the starting speed doubles. For example, if a car doubles its speed from 30 mph to 60 mph, the thinking distance will double from 9 m to 18 m and the braking distance will increase by a factor of four from 14 m to 56 m.

“Although the two-car crash doubles the speed, the energy the crash is transferred to twice the mass resulting in a crash that looks like just one car hitting a wall at 50 mph.” It doesn’t really add any useful explanation other than to point out that the kinetic energy is dependent on the square of the velocity.

No, because kinetic energy is proportional to the square of the speed. So the car at 100mph has 4x the energy of a car at 50mph. The collision of the one car at 100mph has twice the energy of the collision of two cars at 50mph each.