00:01
Hello, in the question we have given that a swimmer bounces straight up from a diving board and falls feet first into a pool.
00:11
So she starts with an velocity that is u is equals to 4 meters per second.
00:17
We are calling this initial velocity as 4 meters per second and her takeoff point is 1 .8 meters above the pool.
00:28
So, let us call this as y o that is equals to 1 .8 meters.
00:36
So how long are her feet in air? so we have to find out the time in air.
00:48
So that is what we need to calculate.
00:51
So we will use the equation over here that is y is equals to y o plus u t plus 1 by 2 a t square.
01:01
So y will be 0 because finally she is coming to earth at ground level.
01:11
Then y o is 1 .8 plus 4 times t minus 1 by 2 times 9 .8 into t square.
01:29
So now if we rearrange this, we will get this as 4 .9 t square minus 4 t minus 1 .8 that is equals to 0.
01:44
Now this is a quadratic equation and if we solve this, so that is by using the method, so it will be t is equals to minus b.
01:56
So minus of minus 4 plus minus square root of b square.
02:05
So b is 4 over here.
02:08
So square root of 4 square minus 4 times a is 4 .9 into 1 .8 divided by 2 times a is 4 .9.
02:26
If we calculate and solve this, we will get the answer as 1 .13 seconds.
02:38
So this is the time that is needed to calculate.
02:46
So for this much time, she's in the air.
02:48
Now the second part is what is her highest point above the board? what is the highest point above the board? so here we will use the equation.
03:02
So at highest point, at highest point, velocity is zero.
03:12
So we will write vf is equals to u plus 80.
03:21
So from here, this is zero.
03:24
So u plus 80.
03:32
So from here, or else we will use this, that is v square is equal to u square plus 2es...