A steel tape measures the length of a copper rod as $90\, cm$ when both are at $10\,^oC$. …….. $cm$ would the tape read for the length of rod when both are at $30\,^oC$ ? $[\alpha _{st} = 1.2\times10^{-5}/^oC$ and $\alpha _{cu} = 1.7\times10^{-5}/^oC]$

A lead bullet at $27\,^oC$ just melts when stopped by an obstacle. Assuming that $25\%$ of heat is absorbed by the obstacle, then the velocity of the bullet at the time of striking is  …….. $m/s$ ( $M.P.$ of lead = $327\,^oC$, specific heat of lead $= 0.03\,cal/g\,^oC$, latent heat of fusion of lead $= 6\,cal/g$ and $J = 4.2\,joule/cal$ )

If a bimetallic strip is heated it will

Three rods of equal length $l$  are joined to form an equilateral triangle $PQR.$  $O$  is the mid point of $PQ.$  Distance $OR$  remains same for small change in temperature. Coefficient of linear expansion for $PR$ and $RQ$  is same, $i.e., \alpha _2$  but that for $PQ$  is $\alpha _1.$ Then

A cylindrical rod with one end in a steam chamber and the outer end in ice results in melting of $0.1 \,\,gm$ of ice per second. If the rod is replaced by another with half the length and double the radius of the first and if the thermal conductivity of material of second rod is $1/4$ that of first, the rate at which ice melts is $gm/sec$ will be