When you double the speed of your vehicle, by how much does its force of impact increase?
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A.
Nine times
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B.
Two times
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C.
Four times Correct
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D.
Three times
The answer is "Four times"
The manual states that when you double the speed of a car, you increase its force of impact four times. Picking two times in B applies the one-for-one rule of thumb drivers use for travel time to a quantity the manual states as squared.
The traps in the wrong answers
A. Nine times
Nine times is the multiplier the manual attaches to tripling the speed, not to doubling it. This answer grabs the larger figure printed in the same paragraph, holding on to the second bullet about impact instead of the first.
B. Two times
Doubling speed does not merely double the impact. The manual attaches a four-times multiplier because force grows with the square of the speed. This answer carries the one-for-one rule of thumb drivers use for judging travel time over to a quantity the manual states as squared.
D. Three times
The manual gives no three-times figure. Doubling produces four times the force and tripling produces nine. This answer splits the gap between the doubling and tripling multipliers as if the increase grew evenly, the way distance grows with time.
This question tests your knowledge of Speed Limits in Florida. Source: Florida Driver Manual, "Speed Limits," p.68..
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