00:02
For number 45, we have this ball that's thrown at an angle of 60, 30 meters per second, and four seconds later, it lands on this cliff that has a height of h, and where we're asked to find h.
00:11
So that's really just the vertical displacement for this problem.
00:15
It starts there, and the problem's going to end here.
00:18
So for part, i am just going to list what i know.
00:21
I know that lands after four seconds.
00:25
I know acceleration due to gravity will be negative 9 .8, because i'm calling up.
00:30
My positive direction.
00:32
When it starts, the vertical, i'm working with just the vertical part here.
00:38
So the vertical component of this would be the cosine.
00:43
So when it starts, my vertical velocity is cosine of 60 times 30.
00:50
And i'm looking for the vertical displacement.
00:56
So i'm going to use my vertical displacement equation.
01:10
I'll plug in my values.
01:30
So for the height of the cliff, i'm getting 25 .5.
01:38
It'd be meters.
01:43
In part b, we want to know what was the maximum height of the ball.
01:53
So for the maximum height of the ball, until that goes up to here.
01:59
So some parts of this are the same.
02:01
I'm looking for the maximum height, so the displacement in this problem.
02:08
Acceleration is still native 9 .8.
02:11
My time is not four, because remember in four seconds, it made it the whole way over here.
02:15
So i don't know the time, but i do know that it's going to stop going up and start coming down.
02:20
So with that very tippy top, the final velocity will be zero for vertical.
02:27
And my v initial is still the same.
02:31
That component.
02:40
So it looks like i'll use the v final squared equation.
02:56
I'll plug in my values.
03:18
I square this, take it to the other side.
03:20
So it's negative, divided by the negative 19 .6.
03:24
And i get 34 .4 meters...