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Old Jul 10th 2014, 09:07 PM   #1
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What does assuming a maximum deceleration mean in the following problem?

In a crash simulation, a car traveling at x m/s can stop at a distance d meters with a maximum deceleration. If the car is traveling at 2x m/s, which of the following statements are true, assuming a maximum deceleration?

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Old Jul 11th 2014, 04:37 AM   #2
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I have no idea why they say it stops with "maximum deceleration." If the problem said the car stops with "constant decelaration" then you can use the standard time-distance formulas, such as v_2^2 - v_^2=2ad. But by using the phrase "maximum deceleration" it seems that they want you to consider the possibility that acceleration is not constant, but rather varies, and could in fact for a brief period of time be virtually unlimited. Perhaps if you post the rest of the problem it would be clearer what they're getting at.
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Old Jul 11th 2014, 10:04 PM   #3
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Hey ChipB,

The rest of the problem went: choose the correct answers. The stopping time is doubled, the stopping distance is doubled, and the stopping distance is quadrupled. The answers were the stopping time is doubled and the distance is quadrupled. I was wondering if maximum deceleration had something to do with velocity final equaling zero? And from there I can set up my kinematics equation so that I can see the relationship in respect to proportion. Thanks ChipB!
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Old Jul 12th 2014, 05:42 AM   #4
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OK, what they mean is to assume that the deceleration is the same in both scenarios - i.e., 'a' is constant. So from v_2^2 -v_1^2 = 2ad, you can see that if v_i is doubled, and v_2 is zero, d is quadrupled. From v_2 = v_1 + at, if v_2 is doubled then t is doubled.
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