00:01
For part a, we can actually set up a quadratic equation.
00:04
We know that here we are going to say that delta y equals vy initial t plus one half a sub y t squared.
00:14
We're going to say that upwards is positive.
00:20
And so if upwards is positive, we say that our change in height would be downwards.
00:29
And in this case, we could say that this would be equalling negative 1 .80 meters.
00:38
So we can say negative 1 .80 meters equals vy initial, which we choose to be positive 4 .00 meters per second times t minus, we can say rather plus 1ā2multplied by negative 9 .80 meters per second squared times t squared.
00:59
As you can see, this is a quadratic, and so you can use your cell function in your t -84, 85, or 89, in order to find t, and the only positive root for t would be equaling 1 .14 seconds.
01:14
This is your answer for how long her feet would be in the air.
01:20
Now, for part v, we want to find essentially what is her highest point above the board.
01:27
So we can say that first v final square, or we can say vy final.
01:34
Vy final squared equals vy initial squared plus two times the acceleration in the y direction times delta y.
01:47
And so we can first say that we're going to choose add the maximum height.
01:51
We know that the final velocity is zero.
01:54
And so we can say that here delta y would be equalling negative vy initial squared over 2 times the acceleration in the wide direction...