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Finding the speed of a bicycle 
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#1
Feb511, 01:23 AM

P: 1

1. The problem statement, all variables and given/known data
Two physics students are trying to detemine the instantaneous speed of a bicycle 5.0 m from the start of a 1000 m sprint. It takes 4s to travel 10m. What is the instananeous speed at the 5m mark? acceleration is constant. (5m mark is 10 m as they start at 5m) X=Distance U=initial speed (U= 0m/s) Note. This is the first thing ive tried since joining year 11 so i am quite a novice and may have just made a stupid error 2. Relevant equations X=ut+1/2at^2 V=U+at 3. The attempt at a solution x=ut+1/2at^2 10=(1/2).(a).(16) 10=8.a a=1.25 V=u+at V=(1.25)(4) V=5m/s But the answers say it 3.5m/s. 1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution 


#2
Feb511, 03:51 AM

P: 22

Your acceleration is correct and you used the equation correctly except for the second part. The time t=4s is for 10m displaced not for 5m. So, let's look at the given:
a = 1.25 m/s^2 Vo = 0 Vf = ? displacement = 5m. Note: You have three given, so you should be able to solve for Vf (instantaneous speed). 


#3
Feb511, 03:57 AM

P: 27

you are right



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