Rekha went to her grandfather’s village for vacation. She saw bullock cart got struck in wet mud and the driver was not able to push it out by himself. Rekha ran to his help and together they pushed it out, but the iron rim of the wheel came out. They tried to put it on the wheel but it was smaller than the diameter of wheel. Suddenly she collected some wood and set them on fire and heated the rim and it slipped on the wheel.
(i) What nature is shown by Rekha ?
(ii) (ii) Name the property of solid used here ?

Explanation

(i) Rekha is a helpful girl. She also has presence of mind as she though of an excellent idea to help cartman.
(ii) Linear expansion of solids i.e., increase in length of solid on heating.
(iii) `L_(T2)=L_(T1)[l+alpha(T_(2)-T_(1))]`
`6.243=6.231[l+1.20xx10^(-5)(T_(2)-27)]`
`T_(2)=187.5^(@)C`