A wax candle floats vertically in a liquid of density twice that of wax. The candle burns at the rate of $4\  cm/hr$ . Then, with respect to the surface of the liquid the upper end of the candle will 

Air is blowing across the horizontal wings of an aeroplane is such a way that its speeds below and above wings are $90\, m/s$ and $120\, m/s$ respectively. If density of air is $1.3\, kg/m^3$, then the pressure difference between lower and upper sides of wings will be ........ $N/m^2$

A spherical solid ball of volume $V$ is made of a material of density ${\rho _1}$ . It is falling through a liquid of density ${\rho _2}\left( {{\rho _2} < {\rho _1}} \right)$. Assume that the liquid  applies a viscous force on the ball that is propoertional to the square of its speed $v$ , i.e., ${F_{{\rm{viscous}}}} =  - k{v^2}\left( {k > 0} \right)$. Then terminal speed of the bal is

If the terminal speed of a sphere of gold (density $\ =\ 19.5 × 10^3\ kg/m^3$ ) is $0.2\ m/s$ in a viscous liquid (density $\ =\ 1.5 × 10^3\ kg/m^3$ ), find the terminal speed of a sphere of silver (density $\ =\ 10.5 × 10^3\ kg/m^3$ ) of the same size in the same liquid ....... $m/s$

A ball of mass $m$ and radius $r$ is gently released in a viscous liquid.The mass of the liquid displaced by it is $m'$ such that $m\, >\, m'$ . The terminal velocity is proportional to

Water rises to a height of $10\, cm$ in capillary tube and mercury falls to a depth of $3.1\,cm$ in the same capillary tube. If the density of mercury is $13.6$ and the angle of contact for mercury is $135^o$, the approximate ratio of surface tensions of water and mercury is