Advertisements
Advertisements
प्रश्न
A raindrop falls near the surface of the earth with almost uniform velocity because
विकल्प
its weight is negligible
the force of surface tension balances its weight
the force of viscosity of air balance its weight
the drops are charged and atmospheric electric field balances its weight.
Advertisements
उत्तर
Air has viscosity. During rainfall, the raindrops acquire acceleration due to gravity. However, the increase in velocity is hindered by the viscous force acting upwards. A gradual balance between the two opposing forces causes the raindrops to attain a terminal velocity, thus, falling with a uniform velocity.
APPEARS IN
संबंधित प्रश्न
A metal sphere of radius 1 mm and mass 50 mg falls vertically in glycerine. Find (a) the viscous force exerted by the glycerine on the sphere when the speed of the sphere is 1 cm s−1, (b) the hydrostatic force exerted by the glycerine on the sphere and (c) the terminal velocity with which the sphere will move down without acceleration. Density of glycerine = 1260 kg m−3 and its coefficient of viscosity at room temperature = 8.0 poise.
Which has greater viscosity, oil or honey? Why?
Distinguish between streamlined flow and turbulent flow.
Define terminal velocity.
Derive the expression for the terminal velocity of a sphere moving in a high viscous fluid using stokes force.
Derive Poiseuille’s formula for the volume of a liquid flowing per second through a pipe under streamlined flow.
A block of Ag of mass x kg hanging from a string is immersed in a liquid of relative density 0.72. If the relative density of Ag is 10 and tension in the string is 37.12 N then compute the mass of Ag block.
From amongst the following curves, which one shows the variation of the velocity v with time t for a small-sized spherical body falling vertically in a long column of a viscous liquid.
The velocity of water in river is 8 km/hr of the upper surface. The river is 12 m deep. If the coefficient of viscosity of water is 10-2 poise then the shearing stress between horizontal layers of water is ______.
The velocity of a small ball of mass M and density d, when dropped in a container filled with glycerine becomes constant after some time. If the density of glycerine is `"d"/2`, then the viscous force acting on the ball will be ______
The velocity of a small ball of mass M and density d, when dropped in a container filled with glycerine becomes constant after some time. If the density of glycerine is `"d"/2` , then the viscous force acting on the ball will be ______.
Is viscosity a vector?
The velocity of a small ball of mass 0.3 g and density 8 g/cc when dropped in a container filled with glycerine becomes constant after some time. If the density of glycerine is 1.3 g/cc, then the value of viscous force acting on the ball will be x × 10-4 N, and the value of x is ______.
[use g = 10 m/s2]
An air bubble of negligible weight having radius r rises steadily through a solution of density σ at speed v. The coefficient of viscosity of the solution is given by ______.
A spherical solid ball of volume V is made of a material of density ρ1. It is falling through a liquid of density ρ2 (ρ2 < ρ1). Assume that the liquid applies a viscous force on the ball that is proportional to the square of its speed v, i.e., `"F"_"viscous"`= -kv2 (k > 0). The terminal speed of the ball is ______.
Define velocity gradient.
An incompressible liquid is flowing through a uniform cross-sectional tube with a velocity 12 cm/ s. If the thickness of liquid layer is 0.8 cm, what is the velocity gradient of that flow of liquid?
State and explain Newton's law of viscosity.
A force of 0.01 N is required to move a flat glass plate of area of 10 cm2 with a uniform velocity of 1 cm/ s over the surface of a liquid 2 mm thick. If the coefficient of viscosity of the liquid is 20 poise, the velocity gradient in the liquid layer is ______.
The dimensions of coefficient of viscosity are ______.
