Final answer:
If the speed of a vehicle increases to 80mph, the braking distance becomes 16 times greater than at 20mph, because braking distance increases with the square of the velocity.
Step-by-step explanation:
When a vehicle's speed is increased to 80mph, both the impact and braking distance are significantly increased compared to when the vehicle is traveling at 20mph. The increase in speed results in a braking distance that is not just doubled, but increases by a factor that is the square of the ratio of the speeds. Since 80mph is four times 20mph, the braking distance at 80mph is 4 squared, or 16 times greater than at 20mph. This is due to the physics of motion, where braking distance is proportional to the square of the velocity.