Kinematics / Acceleration Problem

AI Thread Summary
The discussion revolves around solving a kinematics problem involving an athlete's acceleration during a 100m sprint. The initial calculations for acceleration and velocity yielded values of 2.163 m/s² and 15.141 m/s, respectively, but discrepancies arose when using other kinematic equations. Participants suggested reviewing the formulas and calculations, highlighting potential errors in applying the equations correctly. One user recalculated acceleration to be 2.45 m/s², indicating minor differences in results. The conversation emphasizes the importance of careful application of kinematic equations to ensure accurate results.
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Homework Statement



Q1. In a 100m sprint the athlete can be assumed to accelerate linearly for the first 60m (which takes 7s to cover). For the remaining 40m the running speed is constant.
a) Determine the acceleration over the initial 60m. (5 marks)

b) Draw a graph of
i) acceleration v time (2 marks)
ii) speed v time (2 marks)
iii) distance v time (2 marks)

c) Determine the time taken to complete 100m both graphically and numerically. (4 marks)


Homework Equations



s = ut + 0.5at^2

s = displacement

t = time

a = acceleration

v = u + at

v = velocity

u = initial velocity

t = time

s = 0.5(u+v)t



The Attempt at a Solution



Acceleration = 2.163 m/s^3

Velocity = 15.141m/s


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My problem is when i use other kinematic equations i don't get back to the same values as given in the problem.

when using formula

V^2 = U^2 +2as

i get a different velocty

and when i use formula

s = 0.5at^2

i get a different displacement.

---

So have i solved this corrent?

Any advice on what is the corrent formula or what is the correct answer would be most appreciated... thanks
 
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i think you may have made a numerical calculation error... check numbers again
 
Hey I'm not that good at physics or anything but i'll give it a go...

D=ut + .5 a t^2
60= 0 + 1/2 a 7^2
120 = 49a
a = 2.45 m/s...only slightly different to what you got.
 
Yes, i think you are 100% corrent, i am just going over all the Kinematic equations again.

I believe what i have done is a pre-school error.

I have done 0 * 7 and managed to get 7 =) which its supposed to be 0.

Think its all fixed, thanks...
 
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