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# Physics confusion Can someone explain my answers?

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The first meters of a 100 meter dash are covered in 2 seconds. The sprinter accelerated from rest with a constant acceleration. The remaining 90 m are with the sprinters velocity after the the 2 seconds.

1) what was his acceleration?

for this in class we went over it and talked something about X = Va * t but solving that => 10=Va * 2, The velocuty turns into 5m/s so whats the accelration?

2) find the velocity after the first 2 seconds.

I believe that the answer is 5m/s

3) How long does it take the runner to finish the race.

No idea in notes i just wrote "2s for 10m/s 90m left. 9+2 =11s" Idk where i got the 10m/s from

4) Graph the race

A curve from the origin to 10m and 2s then have a straight line up to 100 and 11s

Sep 12, 2019

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Acceleration = change in velocity / change in time

xf = x0 + v0t + 1/2 a t^2           x 0 = 0    v0 = 0    xf=10       x0= original position or start    v0 = original velocity at start   xf = final position (10m)

10   = 1/2 a (t^2)

10 = 1/2 a (2^2)

20/4 = a      a = 5 m/s^2       ACCELERATION

vf = vo +at

vf = 0 + 5m/s^2 (2 s ) = 10 m/s      VELOCITY

2 seconds + 90m / 10 m/s = 11 seconds     TIME TO FINISH

Sep 12, 2019