Physics-
General
Easy
Question
Water coming out of the mouth of a tap and falling vertically in streamline flow forms a tapering column, i.e., the area of cross-section of the liquid column decreases as it moves down. Which of the following is the most accurate explanation for this
- As the water moves down, its speed increases and hence its pressure decreases. It is then compressed by the atmosphere
- Falling water tries to reach a terminal velocity and hence reduces the area of cross-section to balance upward and downward forces
- The mass of water flowing past any cross-section must remain constant. Also, water is almost incompressible. Hence, the rate of volume flow must remain constant. As this is equal to velocity × area, the area decreases as velocity increases
- The surface tension causes the exposed surface area of the liquid to decrease continuously
The correct answer is: Falling water tries to reach a terminal velocity and hence reduces the area of cross-section to balance upward and downward forces
Related Questions to study
Physics-
A cubical block of wood 10 cm on a side floats at the interface between oil and water with its lower surface horizontal and 4 cm below the interface. The density of oil is 
. The mass of block is
A cubical block of wood 10 cm on a side floats at the interface between oil and water with its lower surface horizontal and 4 cm below the interface. The density of oil is . The mass of block is
Physics-General
Physics-
Water flows through a frictionless duct with a cross-section varying as shown in fig. Pressure p at points along the axis is represented by
Water flows through a frictionless duct with a cross-section varying as shown in fig. Pressure p at points along the axis is represented by
Physics-General
Physics-
The diagram shows a cup of tea seen from above. The tea has been stirred and is now rotating without turbulence. A graph showing the speed v with which the liquid is crossing points at a distance X from O along a radius XO would look like
The diagram shows a cup of tea seen from above. The tea has been stirred and is now rotating without turbulence. A graph showing the speed v with which the liquid is crossing points at a distance X from O along a radius XO would look like
Physics-General
Physics-
A small spherical solid ball is dropped from a great height in a viscous liquid. Its journey in the liquid is best described in the diagram given below by the
A small spherical solid ball is dropped from a great height in a viscous liquid. Its journey in the liquid is best described in the diagram given below by the
Physics-General
Physics-
There are two identical small holes of area of cross-section a on the opposite sides of a tank containing a liquid of density 
. The difference in height between the holes is h. Tank is resting on a smooth horizontal surface. Horizontal force which will has to be applied on the tank to keep it in equilibrium is
There are two identical small holes of area of cross-section a on the opposite sides of a tank containing a liquid of density . The difference in height between the holes is h. Tank is resting on a smooth horizontal surface. Horizontal force which will has to be applied on the tank to keep it in equilibrium is
Physics-General
Physics-
A cylinder containing water up to a height of 25 cm has a hole of cross-section 
in its bottom. It is counterpoised in a balance. What is the initial change in the balancing weight when water begins to flow out
A cylinder containing water up to a height of 25 cm has a hole of cross-section in its bottom. It is counterpoised in a balance. What is the initial change in the balancing weight when water begins to flow out
Physics-General
Physics-
Water is filled in a cylindrical container to a height of 3m. The ratio of the cross-sectional area of the orifice and the beaker is 0.1. The square of the speed of the liquid coming out from the orifice is (g = 10 m/s2)
Water is filled in a cylindrical container to a height of 3m. The ratio of the cross-sectional area of the orifice and the beaker is 0.1. The square of the speed of the liquid coming out from the orifice is (g = 10 m/s2)
Physics-General
Physics-
A body floats in a liquid contained in a beaker. The whole system as shown falls freely under gravity. The upthrust on the body due to the liquid is
A body floats in a liquid contained in a beaker. The whole system as shown falls freely under gravity. The upthrust on the body due to the liquid is
Physics-General
Physics-
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 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
Physics-General
Physics-
A homogeneous solid cylinder of length L
. Cross-sectional area 
is immersed such that it floats with its axis vertical at the liquid-liquid interface with length 
in the denser liquid as shown in the fig. The lower density liquid is open to atmosphere having pressure 
. Then density D of solid is given by
A homogeneous solid cylinder of length L. Cross-sectional area is immersed such that it floats with its axis vertical at the liquid-liquid interface with length in the denser liquid as shown in the fig. The lower density liquid is open to atmosphere having pressure . Then density D of solid is given by
Physics-General
Physics-
A U-tube in which the cross-sectional area of the limb on the left is one quarter, the limb on the right contains mercury (density 13.6 g/cm3). The level of mercury in the narrow limb is at a distance of 36 cm from the upper end of the tube. What will be the rise in the level of mercury in the right limb if the left limb is filled to the top with water
A U-tube in which the cross-sectional area of the limb on the left is one quarter, the limb on the right contains mercury (density 13.6 g/cm3). The level of mercury in the narrow limb is at a distance of 36 cm from the upper end of the tube. What will be the rise in the level of mercury in the right limb if the left limb is filled to the top with water
Physics-General
Physics-
When a body falls in air, the resistance of air depends to a great extent on the shape of the body, 3 different shapes are given. Identify the combination of air resistances which truly represents the physical situation. (The cross sectional areas are the same).
When a body falls in air, the resistance of air depends to a great extent on the shape of the body, 3 different shapes are given. Identify the combination of air resistances which truly represents the physical situation. (The cross sectional areas are the same).
Physics-General
Maths-
5/6 can be represented in percentage as
5/6 can be represented in percentage as
Maths-General
Physics-
A cylindrical vessel of 90 cm height is kept filled upto the brim. It has four holes 1, 2, 3, 4 which are respectively at heights of 20 cm, 30 cm, 45 cm and 50 cm from the horizontal floor PQ. The water falling at the maximum horizontal distance from the vessel comes from
A cylindrical vessel of 90 cm height is kept filled upto the brim. It has four holes 1, 2, 3, 4 which are respectively at heights of 20 cm, 30 cm, 45 cm and 50 cm from the horizontal floor PQ. The water falling at the maximum horizontal distance from the vessel comes from
Physics-General
Physics-
A tank is filled with water up to a height H. Water is allowed to come out of a hole P in one of the walls at a depth D below the surface of water. Express the horizontal distance x in terms of H and D
A tank is filled with water up to a height H. Water is allowed to come out of a hole P in one of the walls at a depth D below the surface of water. Express the horizontal distance x in terms of H and D
Physics-General
