Driver's License Test Prep
Florida Practice Speed Limits

You triple your vehicle's speed. According to the Florida manual, what happens to its force of impact?

  1. A.
    Impact rises by roughly six times.
  2. B.
    Impact grows nine times greater. Correct
  3. C.
    Impact doubles, matching what happens when speed only doubles.
  4. D.
    It matches the speed increase: three times the force.
The Why

The answer is "Impact grows nine times greater."

The Florida manual states that tripling the speed of a car increases its force of impact nine times, because impact grows with the square of speed rather than in step with it. Choice D tempts drivers who assume force of impact rises in direct proportion to speed, so tripling the speed feels like it should triple the impact.

Why the others miss

The traps in the wrong answers

A. Impact rises by roughly six times.

The manual gives nine times for tripling and four times for doubling, with no intermediate figure of six. This answer multiplies the two speed multipliers (double and triple) to land on six, treating the plain-speed factors as combinable rather than reading the manual's separate figure for tripling.

C. Impact doubles, matching what happens when speed only doubles.

The manual says doubling speed makes impact four times greater and tripling makes it nine times greater, so doubling is not the answer at either step. This answer latches onto the word 'double' in the paragraph and pairs it with impact rather than speed, missing that the multiplier for doubled speed is four, not two.

D. It matches the speed increase: three times the force.

Force of impact grows with the square of speed, not in step with it, so tripling the speed of a car increases impact nine times. This answer reads 'triple' in the question as the ready-made answer for impact, applying a straight-line scaling habit that the manual's squared rule overrides.

The Rule

This question tests your knowledge of Speed Limits in Florida. Source: Florida Driver Manual, "Speed Limits," p.68..

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