Brain Teasers
Suspended Meter Stick
A meter stick is suspended exactly at its 45 cm mark from a piece of string, and an 8kg is fixed to the stick and hangs from the 0cm mark. You have six 1kg weights you can hang anywhere on the stick (you can put more than one on the same point if you wish). How can you get the system to balance?
Answer
The turning force of the 8kg is 360The max force on the other side would be if you put all 6 on the 100cm mark - 6*55 turning force = 330 Which isn't enough to balance, so the only way you can to this is by moving the point of suspension of the metre stick!
If you change the point of suspension to the 40cm mark, the 8kg has a turning force of 320; so you could put 5kg at the 100cm mark giving a turning force of 5*60, and put 1kg at the 60cm mark, giving a turn of 1*20 =320 in total
(There are other ways to do this if you chose a different point of suspension, but this is the key to the puzzle.)
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