This java applet shows the advantage of a pulley.
1. There are three sets of pulley.
2. Double click within those block to change its mass.
Right click to increase one unit(gravity g).
Left click to decrease one unit. Mass of those block are shown in blue.
3. You can click within those block and drag it up and down.
4. Gravity pulls down one the block with force Mg.
The rope pulls up on the block with force T(value shown in red).
If the total force acting on the block is zero, it is in equilibrium.
Otherwise, the block is under acceleration(animation starts).
The animation is paused while you press the mouse button.
Harry the painter swings year after year from his bosun's chair.
His weight is 500N and the rope, unknown to him, has a breaking point of 400N.
Why doesn't the rope break when he is supported as shown to the left on the above picture?
One day Harry is painting near a flagpole, and,
for a change he ties the free end of the rope to the flagpole instead of to his chair as shown to the right.
Why did Harry end up taking his vacation early? (Not really funny! Too bad!)