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jehan4141
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Please interpret this problem as you will. My professor and I seem to have different interpretations of this problem.
A runner hopes to complete the 10, 000 meter run in less than 30 minutes. After exactly 27.0 minutes, there are still 1100 meters to go. For how many seconds must then the runner accelerate at 0.20 m/s2 to achieve the desired time?
My interpretation was that he can run the entire 10,000 meters in LESS than 30 minutes. So this is what I did:
1. I found that starting from rest, he can run the first 8900 meters in 27 minutes.
10000-1100 = 8900 m
t = 27(60) = 1620 seconds
Thus the average velocity is v = x/t = 8900/1620
v=5.49382716 m/s
2. I know that when this velocity is reached, he starts to accelerate at a = 0.2 m/s2. So I call it Vi.
Starting from Vi = 5.49 m/s, he has 1100 meters left to run.
Using the equation x = xo + Vit + 0.5at2 I get
1100 = 5.49t + 0.5(0.2)t2
Cleaned up you get
0.1t2 + 5.49t - 1100 = 0
Solve. T = 80.94928247
Is my answer correct? My teacher's answer is different than mine. Did I misinterpret the problem somewhere? How is your interpretation? Thank you!
A runner hopes to complete the 10, 000 meter run in less than 30 minutes. After exactly 27.0 minutes, there are still 1100 meters to go. For how many seconds must then the runner accelerate at 0.20 m/s2 to achieve the desired time?
The Attempt at a Solution
My interpretation was that he can run the entire 10,000 meters in LESS than 30 minutes. So this is what I did:
1. I found that starting from rest, he can run the first 8900 meters in 27 minutes.
10000-1100 = 8900 m
t = 27(60) = 1620 seconds
Thus the average velocity is v = x/t = 8900/1620
v=5.49382716 m/s
2. I know that when this velocity is reached, he starts to accelerate at a = 0.2 m/s2. So I call it Vi.
Starting from Vi = 5.49 m/s, he has 1100 meters left to run.
Using the equation x = xo + Vit + 0.5at2 I get
1100 = 5.49t + 0.5(0.2)t2
Cleaned up you get
0.1t2 + 5.49t - 1100 = 0
Solve. T = 80.94928247
Is my answer correct? My teacher's answer is different than mine. Did I misinterpret the problem somewhere? How is your interpretation? Thank you!