Physics-
General
Easy
Question
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
- Increase of 12.5 gm-wt
- Increase of 6.25 gm-wt
- Decrease of 12.5 gm-wt
- Decrease of 6.25 gm-wt
The correct answer is: Decrease of 12.5 gm-wt
Let A = The area of cross section of the hole
v = Initial velocity of efflux
d = Density of water,
Initial volume of water flowing out per second = Av
Initial mass of water flowing out per second = Avd
Rate of change of momentum = Adv2
Initial downward force on the flowing out water = Adv2
So equal amount of reaction acts upwards on the cylinder.
\ Initial upward reaction =
[As 
]
Initial decrease in weight 
gm-wt.
Related Questions to study
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
Physics-
An L-shaped glass tube is just immersed in flowing water such that its opening is pointing against flowing water. If the speed of water current is v, then
An L-shaped glass tube is just immersed in flowing water such that its opening is pointing against flowing water. If the speed of water current is v, then
Physics-General
Physics-
A liquid flows through a horizontal tube. The velocities of the liquid in the two sections, which have areas of cross-section 
and 
, are 
and 
respectively. The difference in the levels of the liquid in the two vertical tubes is h
A liquid flows through a horizontal tube. The velocities of the liquid in the two sections, which have areas of cross-section and , are and respectively. The difference in the levels of the liquid in the two vertical tubes is h
Physics-General
Physics-
In this figure, an ideal liquid flows through the tube, which is of uniform cross-section. The liquid has velocities
and 
, and pressure PA and PB at points A and B respectively
In this figure, an ideal liquid flows through the tube, which is of uniform cross-section. The liquid has velocities and , and pressure PA and PB at points A and B respectively
Physics-General
Physics-
A liquid flows in a tube from left to right as shown in figure. and are the cross-sections of the portions of the tube as shown. Then the ratio of speeds 
will be
A liquid flows in a tube from left to right as shown in figure. and are the cross-sections of the portions of the tube as shown. Then the ratio of speeds will be
Physics-General
Physics-
A ball of radius r and density r 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 h, the value of h is given by
A ball of radius r and density r 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 h, the value of h is given by
Physics-General
Physics-
In the following fig. is shown the flow of liquid through a horizontal pipe. Three tubes A, B and C are connected to the pipe. The radii of the tubes A, B and C at the junction are respectively 2 cm, 1 cm and 2 cm. It can be said that the
In the following fig. is shown the flow of liquid through a horizontal pipe. Three tubes A, B and C are connected to the pipe. The radii of the tubes A, B and C at the junction are respectively 2 cm, 1 cm and 2 cm. It can be said that the
Physics-General
