Physics Check?
A swimmer is 1.8 meters tall. She dives into the pool and swims her race with a constant acceleration of .25m/^2. How long does it take her to pass the backstroke flags that are 20 meters away?
When I did it, i got 13.2 seconds. Could someone who is good at physics please check it and see if i did it wrong? Thanks so much.
Update:I ment to say .25m/s^2!
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you are correct, and elizabeth is lame
A swimmer has to swim the distance 20 m + 1.8 m = 21.8 m, in order to pass the flags (it is because she dives verticaly, I assume, at the edge of the pool and so she has to swim 20 m plus her own height)
One of the kinematics equations for uniformly accelerated motion is:
s = 1/2 x a x t2
If you solve for t, you get:
t = sqrt (2 x s / a) = 13.2 s ---> you were probably right!
You never told the answer so I don't know if I got it right, but I got 12.1s. I think you may have to account for her height by subtracting it form the total distance to get 18.2m instead of 20.
No. First of all, you can't use d=vt when there is acceleration. (Your distance would have been the distance the car travelled if it kept that speed up for THE WHOLE TIME.) Second, the acceleration formula is (v2-vo)/t (not over d). For part a, use d=vot+1/2at^2.
I made it 12.1s. You have to account for her height by subtracting it form the total distance to get 18.2m instead of 20m.
physics is lame =]