What happens to your stopping distance when you double your speed from 20 to 40 mph?

When you double your speed, the stopping distance increases significantly due to the physics of motion and the kinetic energy involved. At 20 mph, your vehicle has a certain amount of kinetic energy, and when you increase your speed to 40 mph, that kinetic energy increases by a factor of four, assuming mass remains constant.

The formula for kinetic energy is ( KE = \frac{1}{2} mv^2 ), where ( m ) is mass and ( v ) is velocity. When you increase the speed from 20 to 40 mph, you are effectively squaring the velocity term in the formula (since ( 40^2 = 1600 ) and ( 20^2 = 400 )), resulting in four times the kinetic energy.

As a consequence, the required stopping distance also increases because a vehicle requires more distance to come to a complete stop when it is traveling at higher speeds. Factors such as vehicle weight, road conditions, and tire traction also play a role; however, the fundamental principle remains that doubling the speed results in quadrupling the stopping distance. Therefore, the correct understanding is that when speed is doubled, the stopping distance becomes four times greater.