Advertisements
Advertisements
प्रश्न
A raindrop falls near the surface of the earth with almost uniform velocity because
पर्याय
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
Fill in the blanks using the word(s) from the list appended with each statement
Viscosity of gases. .. with temperature, whereas viscosity of liquids . . . with temperature (increases / decreases)
A spherical ball is dropped in a long column of a viscous liquid. The speed of the ball as a function of time may be best represented by the graph
Which has greater viscosity, oil or honey? Why?
With an increase in temperature, the viscosity of liquid and gas, respectively will __________.
What is Reynold’s number? Give its significance.
Define terminal velocity.
Write down the expression for Stoke’s force and explain the symbols involved in it.
Two streamlines cannot cross each other. Why?
Derive the expression for the terminal velocity of a sphere moving in a high viscous fluid using stokes force.
Choose the CORRECT statement.
The tangential force or viscous drag on any layer of the liquid is directly proportional to the velocity gradient `"dv"/"dx"`. Then the direction of dx velocity gradient is ____________.
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 ______.
Analogy
Viscous force: ______:: Buoyant force: ______.
Clouds float in the air due to ______.
Is viscosity a vector?
The coefficient of apparent expansion of mercury in a glass vessel is 153 × 10-6/°C and in a steel vessel is 144 × 10-6/°C. If α for steel is 12 × 10-6/°C, then that of glass is ______.
A liquid of density ρ and coefficient of viscosity η flows with velocity v through a tube of diameter D. A quantity `"R" = (rho"vD")/η`, determines whether the flow will be streamlined or turbulent. R has the dimension of ______.
Define velocity gradient.
The dimensions of coefficient of viscosity are ______.
