00:01
All right, so let's say we have an atwood machine where we have two blocks like this.
00:05
We'll call us block 1 and block 2.
00:08
Block 1, we're told, has a mass of 1 .3 kilograms.
00:13
Block 2 has a mass of 2 .8 kilograms, and we want to find the acceleration and the tension in the cords for each of these.
00:21
So the free body diagram for each of these looks identical.
00:25
You have the weight of the block going down, and then you have the tension going up.
00:31
So for part a, if we write out newton's second law for each of these, we'll have m1a, and block one is lighter than block two or less massive, so it's going to move upward.
00:41
So it'll go in the same direction as the tension, and so the weight is given by mg.
00:47
And if we do the same thing for the second block, it should look the same, but we'll just reverse the sign of the acceleration, because if one block moves up, the other has to move down.
00:56
And so if we add both of these terms together, both of these equations together, we'll get the familiar result that this is m2 minus m1 over m1 plus m2 times g...