00:01
In this example, we're going to be looking at motion on the surface of the moon.
00:05
We have an astronaut.
00:07
The astronaut has a height h of 6 .5 feet.
00:12
He is going to throw a baseball straight upward with an initial velocity of the initial equals 50 .0 feet per second.
00:24
We know the acceleration due to gravity on the surface of the moon, ag, equal.
00:31
2 .7 feet per second squared and that's negative.
00:38
I want to find the time it will take the ball to get to 14 feet above the surface of the moon and i want to find out how long it'll take for the ball to hit the surface of the moon.
00:51
All right.
00:52
So we have initial velocity.
00:54
We have our initial position.
00:56
We have our acceleration.
00:58
So we can use the equation.
01:00
Y final equals y.
01:02
Initial plus v initial t plus one half a t squared just like we do on the earth where we have a different value for acceleration that's the only difference right so my final position is 14 feet my initial position is 6 .5 feet initial velocity is 50 acceleration is negative 2 .7 so i have an equation that looks like 14 equals 6 .5 plus 50 t minus 1 half 2 .7 t squared.
01:40
All right, this is just a quadratic equation that we can solve for t and i get t equals 0 .151 and 18 .37 seconds.
02:00
All right.
02:01
So the 0 .151 is on the up, right, and the 18 .37 is on the way down.
02:11
So that's my 14 feet above the surface.
02:16
Now, to find the total time, the ball will be in the air.
02:21
First i'm going to find out how high it goes...