00:01
Okay, so we're told that the vertical displacement that the ball gets is 7 .5.
00:06
And we're told that the final velocity in the x direction is going to be 31 .35 cos 26 .5.
00:18
And in the y direction, it's going to be going downwards.
00:21
It's going to be minus 31 .35 sine 26 .5.
00:30
And we want to know the initial speed of the ball.
00:33
So the initial speed which i'll call u, the magnitude of it is given by the square of the x component plus the square of the y component.
00:41
Now in order to find what these are we just need to write out these values that we have so i'll just pop down the values so here this is 28 .06 if you run it through a calculator and here it's minus 13 .99.
00:56
And we just need to write these out in terms of their equations.
01:00
So here we know that the vertical displacement is given by the initial vertical velocity times the time minus a half times newton's gravitational acceleration g times the time squared.
01:12
We also know that the horizontal velocity always stays the same and that the vertical velocity at the end is equal to the vertical velocity at the beginning minus the gravitational acceleration constant g times the time.
01:28
So we've already got ux so we just need uy and in order to do that we're going to substitute uy into, so we're going to rearrange equation three for uy substitute it into equation one and use that to solve for t and then plug that back into equation three...