A vertical steel post of diameter 25cm and length 2.5m supports a weight of 8000kg. Find the change in length produced.
A 5m long aluminium wire (Y=7×1010Nm−2) of diameter 3mm supports a 40kg mass. In order to have the same elongation in the copper wire (Y=12×1010Nm−2) of the same length under the same weight, the diameter of the copper wire should now be (in mm).