Physics Help Forum Motion Basics

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 Jan 31st 2011, 02:59 AM #1 Junior Member   Join Date: Jan 2011 Posts: 9 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?
 Jan 31st 2011, 03:11 AM #2 Member   Join Date: Oct 2010 Location: Sri Lanka Posts: 63 depends on the acceleration that the police car can achieve
 Jan 31st 2011, 03:15 AM #3 Junior Member   Join Date: Jan 2011 Posts: 9 Sorry the police car begins to accelerate at a rate of 4m/s^2 immediately after the motorbike has passed it.
 Jan 31st 2011, 03:29 AM #4 Member   Join Date: Oct 2010 Location: Sri Lanka Posts: 63 apply s=ut+(1/2)at^2 for both the vehicles since there are two unknows(s and t)
 Jan 31st 2011, 03:45 AM #5 Junior Member   Join Date: Jan 2011 Posts: 9 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.
 Jan 31st 2011, 04:10 AM #6 Member   Join Date: Oct 2010 Location: Sri Lanka Posts: 63 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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