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A raindrop with radius $R=0.2\, {mm}$ fells from a cloud at a height $h=2000\, {m}$ above the ground. Assume that the drop is spherical throughout its fall and the force of buoyance may be neglected, then the terminal speed attainde by the raindrop is : (In ${ms}^{-1}$)
[Density of water $f_{{w}}=1000\;{kg} {m}^{-3}$ and density of air $f_{{a}}=1.2\; {kg} {m}^{-3}, {g}=10 \;{m} / {s}^{2}$ Coefficient of viscosity of air $=18 \times 10^{-5} \;{Nsm}^{-2}$ ]
A thin uniform tube is bent into a circle of radius $r$ in the virtical plane. Equal volumes of two immiscible liquids, whose densities are ${\rho _1}$ and ${\rho _2}\left( {{\rho _1} > {\rho _2}} \right)$ fill half the circle. The angle $\theta$ between the radius vector passing through the common interface and the vertical is
A wooden cube first floats inside water when a $200\,g$ mass is placed on it. When the mass is removed the cube is $2\,cm$ above water level. The side of cube is ........ $cm$
A ball of radius $r $ and density $\rho$ falls freely under gravity through a distance $h$ before entering water. Velocity of ball does not change even on entering water. If viscosity of water is $\eta$, the value of $h$ is given by
A machine is blowing spherical soap bubbles of different radii filled with helium gas.It is found that, if the bubbles have a radius smaller than $1\,cm$, then they sink to the floor in still air. Larger bubbles float in the air. Assume that the thickness of the soap film in all bubbles is uniform and equal. Assume that the density of soap solution is same as that of water $\left(=1000 \,kg m ^{-3}\right)$. The density of helium inside the bubbles and air are $0.18 \,kg m ^{-3}$ and $1.23 \,kg m ^{-3}$, respectively. Then, the thickness of the soap film of the bubbles is .......... $\mu m$ (Note $1 \,\mu m =10^{-6} \,m$ )
A steady flow of water passes along a horizontal tube from a wide section $X$ to the narrower section $Y$, see figure. Manometers are placed at $P$ and $Q$ at the sections. Which of the statements $A, B, C, D, E$ is most correct?
A wooden block, with a coin placed on its top, floats in water as shown in fig. the distance $l $ and $h$ are shown there. After some time the coin falls into the water. Then
A large open tank has two holes in the wall. One is a square hole of side $L$ at a depth $y $ from the top and the other is a circular hole of radius $ R$ at a depth $ 4y $ from the top. When the tank is completely filled with water the quantities of water flowing out per second from both the holes are the same. Then $ R$ is equal to