Two spheres of same size are made from copper and iron respectively. Find the ratio between their masses. (Density of copper `8,900kg//m^3` and iron `7,800kg//m^3`)

A sphere of radius 1cm is made from silver. If the mass of the sphere is 33g, Find the density of silver. (Take pi =3.14)

(a) Esttimate the average drift speed of conduction electrons in a copper wite of cross-secttonal area 1.0 xx 10 ^(-7)m^(2) carrying a current of 1.5A. Assume the each copper atom contrbutes roughly one conduction electron. The density of copper is 9.0 xx 10 ^(3)kg//m^(3), and its atomic mass is 63.5 u. (b) Compare the drift speed obyained above with, (1) thermal speeds of copper atoms at ordinary temperaturtes. (ii) speed of propagation of electric field along the conductor which causes the drift motion.

A copper rod of length 20cm and cross-sectional area 2mm^(2) is joined with a similar aluminium rod as shown in figure .Find the resistance of the combination between the ends, Resistivity of copper =1.7xx10^(-8)(Omega)m and that of aluminium =2.6xx10^(-8)(Omega)m .

Estimate the volume of a water molecule using the data of one molecule( density of water = 1000kg //m^3) What is its approximate size?

If two masses m_1" and "m_2 are experiencing the same force, then the ratio of respective acceleration is

Two blocks each having a mass of 3.2 kg are connected by a wire CD and the system is suspended from the ceiling by another wire AB . The linear mass density of the wire AB is 10 g /m and that of CD is 8 g m^-1. Find the speed of a transverse wave pulse produced in AB and in CD.

A body of mass 6 kg is floating in a liquid with (2)/(3) of its volume inside the liquid. Find (i) buoyant force acting on the body and (ii) ratio between the density of the body and density of liquid. [Take g=10m//s^(2) ].