- #1
Elbobo
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Homework Statement
A runner hopes to complete the 10,000-m run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go.
The runner must then accelerate at 0.20 m/s2 for how many seconds in order to achieve the desired time?
Homework Equations
vf = vo + at
avg velocity = (vf + vo) /2
d = vo)t + (1/2) at2
vf2 = vo2 + 2ad
The Attempt at a Solution
Most of my solutions just wind up at 0 = 0 or a = a... In other words, I'm not doing anything wrong, but it's that I can't think of any other way to solve it.
d1 = 8900 m
t = 1620 s
d2 = 1100 m
avg velocity = 8900 / 1620 = A
(I took this route so I could find the instantaneous velocity at t = 1620s, which I though would lead up to another part that could solve the problem)
A = (vf+ vo) / 2
2A - vf = vo
a = [vf - (2A - vf)] / t
a = (2vf - 2A) /t
vf2 = (2A - vf)2 + 2[ (2vf -2A) /t] d1
(which results in)
0 = 0
I've been thinking about this problem for a loooong time, but I can't figure out another way to solve it.