Colorado CDL Practice Test

If you triple your speed, how much greater is the impact and braking distance?

1. 3x greater

2. 6x greater

3. 9x greater

4. 12x greater

The correct answer is: 9x greater

When a vehicle’s speed is increased, the effects on stopping distance and impact are not linear, but rather exponential. Specifically, when the speed of a vehicle is tripled, the kinetic energy, which is a crucial factor in impact force, increases by the square of the speed. The kinetic energy of an object is calculated using the formula: \[ KE = \frac{1}{2}mv^2 \] where \( m \) is the mass and \( v \) is the speed. If the speed is tripled (for instance, from \( v \) to \( 3v \)), the kinetic energy becomes: \[ KE_{new} = \frac{1}{2}m(3v)^2 = \frac{1}{2}m(9v^2) = 9 \times KE_{original} \] This shows that impact energy increases by a factor of nine, making the consequence of an accident much worse at higher speeds. In addition, stopping distance is influenced by the speed at which a vehicle travels. The braking distance is often calculated as proportional to the square of the speed. So if the speed is increased threefold, the stopping distance can also be expected to increase by a factor