Posted by John on .
The engine weighs 4500 newtons and it is lifted 1.5 meters up by the block and tackle system. To accomplish this, the mechanic must apply a force of 225 newtons while pulling a total of 37.5 meters of chain through the block and tackle pulley system. What is the work done by the block and tackle system?

physics 
drwls,
Force applied x distance = 225 x 37.5 = 8438 J
is the work done. Only 4500*1.5 = 6750 J is used raising the engine. The rest was used overcoming friction.
The block and tackle is not 100% efficient. The efficiency is 80%