00:01
So in this problem we have this section of pulleys and we want to see how they behave.
00:06
We need to find the tension in the string and everything related.
00:11
So we can draw this a bit closer.
00:15
So the pulley one pulley is attached to the string here and then we have the one where the mass is so the string pulls through.
00:21
We're pulling some force p on it and the string wraps around the pulleys and then below this we have our 600 newton weight.
00:35
So to understand this problem, we first need to talk about how we represent strings in this kind of context.
00:40
So when we have a string, we say it's ideal, and so it doesn't stretch.
00:50
It is mass lifts, so we don't have to worry about that.
00:54
And the result of this and equilibrium means that the force is constant through the string.
01:02
So we've applied force p to the end of the string here, and what that requires is that in every bit of this string, the tension force is p.
01:11
All the way through.
01:12
So let's look at a free by diagram of this bottom pulley.
01:16
Now we do need to represent it as a circle because we have forces offset here.
01:20
Everywhere there's a string, we can replace it with a force of force p because we said we have an ideal string here.
01:29
And then we have our weight 600 newtons down below and i think we're taking the pulleys to be mass list, but we don't have any information about them...