00:01
For number 41, we're given that projectiles launched at an angle of theta, and v -initial v .0 will be the velocity.
00:08
And we're to find an expression for the height.
00:11
So i know that for the vertical motion, i know that acceleration be negative g, the initial velocity will be this component.
00:26
So that's the opposite side.
00:28
So i'll use sine.
00:30
So sine of theta times v.
00:36
The, it's going to go up until it stops, so v final will be zero if i'm doing just the way up, and i'm looking for the vertical displacement.
00:48
So i'm going to use the f squared equation.
01:03
Vf would be zero, the i will be this, that gets squared, so i'm going to put that squared and that squared to negative g times d, and i'm solving for this d.
01:21
So i'm solving for this d.
01:22
So so imagine to take this all to this side, so it's positive.
01:26
You get the d by itself.
01:35
So i bring the 2 and the g over here.
01:41
So this would be the vertical displacement or the height.
01:44
So there's my expression.
01:46
So that's my answer to part a.
01:56
For part b, i'm going to know i'm given the velocity of a baseball is 33 .6 meters per second.
02:07
And then i'm to find how high and how far it goes when it's thrown at 30 degrees, 45 degrees, and 60 degrees.
02:18
So i have my expression for height.
02:21
I could do that for all of them.
02:23
Maybe i'll go ahead and do that.
02:24
So i'm just plugging into this equation for each one of those.
02:27
So i'm going to have sine squared 30 degrees, 33 .6 squared over 2 .3 .6 squared over 2.
02:45
Times 9 .8.
02:48
For that one i get 14 .4 meters at 45 degrees.
02:57
So same thing here.
02:58
All i'm doing is changing is to 45.
03:13
For that one i get 28 .8 meters.
03:21
And then same thing for 60 degrees.
03:39
And for that i get 43 .2 meters.
03:50
So now i need to find how far it goes at each one of these angles.
03:54
So i'm just going to come up with an expression for range now.
03:59
There is a range equation, but i like to derive my own equations.
04:04
So i'm just going to come back to this information here and instead get an expression for time.
04:15
So instead of finding this place, i'm going to find time.
04:17
So i'm going to use, for that, i'm going to use the acceleration equation.
04:26
I know my acceleration is negative g...