USAREUR Practice Exam

If driving speed is doubled, how much greater is the force of collision?

1. Twice as great

2. Three times as great

3. Four times as great

4. Five times as great

The correct answer is: Four times as great

When driving speed is doubled, the kinetic energy of the moving vehicle, which is directly related to the force of collision, increases by a factor related to the square of the velocity. Kinetic energy is calculated using the formula \( KE = \frac{1}{2} mv^2 \), where \( m \) is mass and \( v \) is velocity. When the speed is doubled, the new kinetic energy becomes \( KE' = \frac{1}{2} m (2v)^2 = \frac{1}{2} m (4v^2) = 4 \times \frac{1}{2} mv^2 \). This shows that the kinetic energy—and thus the potential force of collision—quadruples when the speed is doubled. Therefore, the force of collision increases four times, making the correct answer four times as great when the driving speed is doubled. This principle highlights the importance of speed in collision scenarios, demonstrating how increases in velocity dramatically affect collision forces.