Two children are at opposite ends of an aluminium rod. One strikes the end of the rod with a stone. Find the ratio of times taken by the sound wave in air and in aluminium to reach the second child.

The ends of a rod of length l move on two mutually perpendicular lines. Find the locus of the point on the rod which divides it in the ratio 1 : 2.

Point masses m_1 and m_2 are placed at the opposite ends of a rigid rod of length L, and nelgligible mass. The rod is to be set rotating about an axis perpendicular to it. Find the position on this rod through which the axis should pass in order that the work required to set the rod rotating with angular velocity omega_0 should be minimum.

Saurabh takes 15 minutes to reach school from his house and Sachin takes one hour to reach school from house.Find the ratio of the time taken by Saurabh to the time tken by Sachin

A stone is dropped in a 44.1 m deep well. If the sound produced by striking of stone with the water surface is heard after 3.13 s then find the velocity of wave in air.

One end of a cylinrical rod is grounded to a hemispherical surface or rdius R=20 mm.It is immersed in water of refractive ndex 1.33.If the refractive index of the rodd is 1.50,find the position of the image of an object placed on the axis of the rod inside water at 10 cm from the pole.

Rachel, an engineering student, was asked to make a model shaped like a cyclinder. with two cones attached at its two ends by using a thin aluminium sheet. The diameter of the model is 3 cm and its length is 12 cm. If each cone has a height of 2 cm, find the volume of air contained in the model the Rachel made. (Assume the outer and inner dimensions of the model to be nearly the same.)