00:01
A ball is being thrown directly, vertically, up in the air at some unknown speed.
00:05
And we're going to use an example here.
00:06
So i'm just going to put that as 20 meters per second.
00:09
We made this up, so don't get confused.
00:11
We want to know at maximum height, what is its acceleration and velocity? well, the first one will be acceleration.
00:20
When an object is in the air and we're ignoring the air resistance and any other force that may be affecting the ball, the only acceleration it will experience is that due to gravity.
00:30
And so we're going to put gravity.
00:32
Because as you throw a ball in the air, it starts to slow down as it goes up, and it speeds up as it comes back down, and that is all due to gravity.
00:39
The gravity on earth is simply negative because it points downward, 9 .8 meters per second squared.
00:46
Meters per second means every second it slows down, 9 .8 meters per second.
00:52
Slows down when it's going up, speeds up when it's coming down.
00:55
And so if we threw this ball at 20 meters per second, one second later, we're going to round this to 10.
01:01
So assume gravity is basically 10.
01:03
That means every second going up, it's going to slow down 10 meters per second.
01:08
And so now it's moving at 10 meters per second.
01:11
Another second later, it's going to be moving at zero meters per second.
01:16
And it won't continue moving up because it has run out of velocity.
01:20
And so maximum height, the velocity in the vertical will always be zero.
01:24
That is why it is maximum height.
01:27
So that's your answers for the first part.
01:29
Now we're going to talk about when it comes back to.
01:31
Down.
01:32
Again, it is still experiencing acceleration due to gravity...