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Old Jan 31st 2011, 03:59 AM   #1
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Motion Basics

A speeding motorbike travels past a stationary police car at a speed of 35m/s. The police car starts accelerating at this rate until it has passed the bike.

1) How far dies the police car travel before it overtakes the motorbike?
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Old Jan 31st 2011, 04:11 AM   #2
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depends on the acceleration that the police car can achieve
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Old Jan 31st 2011, 04:15 AM   #3
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Sorry the police car begins to accelerate at a rate of 4m/s^2 immediately after the motorbike has passed it.
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Old Jan 31st 2011, 04:29 AM   #4
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apply
s=ut+(1/2)at^2

for both the vehicles since there are two unknows(s and t)
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Old Jan 31st 2011, 04:45 AM   #5
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I applied what you done, i solved the time of it, that came out to be 17.5 seconds, which is correct. However for the distance(s) i substituted the time into the s=ut+1/2at^2 and it came out as 1225............This is not an ambiguous answer. I substituted the time into the first half of the equation the answer was 612.5, which is the correct answer. So i am a bit confused with the answers.
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Old Jan 31st 2011, 05:10 AM   #6
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when applying the equation to the police vehicle, u(initial velocity) is 0

when applying the equation to the motorbike, a(acceleration) is 0

you must've done the following

s=35(17.5)+(1/2)(4)(17.5)^2 = 1225 which is wrong

it has to be either s= 0(17.5)+(1/2)(4)(17.5)^2 (for the police vehicle)

or s=(35)(17.5) (for the motorbike)
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