00:01
Okay, you're playing to the ball with a friend and you hit the ball so that it begins traveling in a circular pack.
00:09
So let's draw, here's our pole, and here's a string, at the end of it is the ball.
00:18
Okay, the ball is 1 .2 meters from the pole, so that's this distance here we're going to call l.
00:31
There's a speed of 3 .7 meters per second and a mass of 0 .42 kilograms, and the rope makes a 49.
00:38
Degree angle with the pole.
00:45
Okay, and that's pulled.
00:45
It's a 90 degree there.
00:47
And that means this would be 41 degrees.
00:51
Okay, we're going to need that 41 degrees here in a second.
00:54
So let me just show where i got that.
00:57
Remember, in a triangle, if you add all the angles, so 49 plus 90, plus the unknown angle, we'll just call it question mark, that equals 180.
01:09
So if you solve for the unknown angle you get 41 degrees.
01:14
Okay, so what's the tension in the rope? well, let's draw the forces acting on the ball.
01:21
So gravity is pointed down, tension is pointed up into the right.
01:27
And with this picture i've drawn here, it's like the ball is it's either coming right out of the page at you or going right into the page.
01:38
Okay, so let's come up with some directions here.
01:42
Say y is up, x is towards the pole.
01:46
So let's say the sum of the forces in the x equals m a.
01:52
What are our x forces just tension? it's the x component of tension, so t cosine 41...