2nd time posting bc i still need HELP! PHYSICS!!!!
posted by MC on .
The velocity of a diver just before hitting the water is 8.6 m/s, where the minus sign indicates that her motion is directly downward. What is her displacement during the last 0.86 s of the dive?
im so stuck. i tried this problem several times, and my answers werent correct. please help me.

I had a problem similar to this but I was using 11.4 m/s and 1.35 s. You can use my calculations below and just plug in your numbers.
Velocity of diver just before hitting the water,Vf =  11.4 m/s
Time, t = 1.35 s
Velocity of diver before 1.35 s = Vi
Vf = Vi  g t
 11.4 = Vi  9.8 * 1.35
 11.4 = Vi  13.23
Vi = 13.23  11.4
= 1.83 m/s
Displacement during 't' s , S = [ ( Vi + Vf ) /2 ] t
= [ ( 1.83  11.4 ) / 2 ] * 1.35
=  6.46 m 
Vf=Vo+gt where Vf is velocity just before hitting water, and Vo is at the start of the .86
8.6m/s=Vo9.8(.86)
Vo= 8.6+8.43=.172
So the average velocity is 8.49, displacement then is downward 8.49*.86 meters