You want to prove the law of conservation of energy to a friend. for your demonstration you show that you can use a block and pulley machine to lift 100n with only 20n of input force. what would you say to your friend to explain how is this possible?

Pulleys help reduce the force needed by changing its direction; however, the direction of the movement is also changed. Therefore, the pulley's rope must be pulled further than the actual displacement of the block. Say if the block is raised by 1 meters, then the rope would have to be pulled 5 meters, thus conserving energy.

Explanation:

Organs are groups of tissues that work together to perform a certain function. Organ systems represent the highest level of an organism's bodily organization. They are made up of groups of organs that work together in order to carry out a certain function.