Tag: pressure in liquids and gases

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Questions Related to pressure in liquids and gases

Multiple choice physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

A Liquid of density p is coming out of a hosepipe of the radius with horizontal speed $\upsilon $  and hits a mesh.  50 % of the liquid passes through the mesh unaffected.  25 % loses all of its momentum and 25 % comes back with the same speed.  The resultant pressure on the mesh will be: 

  1. $\frac{3}{4}p\upsilon ^{2}$

  2. $p\upsilon ^{2}$

  3. $\frac{1}{2}p\upsilon ^{2}$

  4. $\frac{1}{4}p\upsilon ^{2}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Force on mesh = change in momentum per unit time. 50% pass through (no change), 25% stop (delta p = mv), 25% rebound (delta p = 2mv). Total force = 0.25(mv) + 0.25(2mv) = 0.75mv. Pressure = Force/Area = 0.75 * rho * v^2.

Multiple choice physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

Since pressure is force per unit area, it is a vector quantity.

  1. True

  2. False

  3. Ambiguous

  4. Data insufficient
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Answer is B.

Pressure is defined as force per unit area. It is usually more convenient to use pressure rather than force to describe the influences upon fluid behavior. The standard unit for pressure is the Pascal, which is a Newton per square meter.
Therefore, pressure is a scalar quantity, not a vector quantity. It has magnitude but no direction sense associated with it. Pressure acts in all directions at a point inside.
Hence, the statement is false.

Multiple choice physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

We sit in the room with windows open. Then

  1. Air pressure on the floor of the room equals the atmospheric pressure but the air pressure on the ceiling is negligible

  2. Air pressure is nearly the same on the floor, the walls and ceiling

  3. Air pressure on the floor equals the weight of the air column inside the room (from floor to ceiling) per unit area

  4. Air pressure on the walls is zero since the weight of air acts downward
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Answer is B.

Varying air pressures in buildings result from uncontrolled air flow patterns.When a space is under a positive air pressure, indoor air will be pushed outward in the walls, floor and ceiling. When a space is under a negative pressure, air will be pulled inward through the walls, floor and ceiling. 
In this case, the windows in the room are open and so there is free flow of air in and out of the room. 
Hence, air pressure is nearly the same on the floor, the walls and ceiling.

Multiple choice physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

In a hydel station, the motion produced in turbines is due to the

  1. burning of coal

  2. burning of diesel

  3. flow of water

  4. production of steam
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Water flowing in the river is comprised of kinetic energy and potential energy. In hydroelectric power plants the potential energy of water is utilized to produce electricity.

The dam is the most important component of hydroelectric power plant. The dam is built on a large river that has abundant quantity of water throughout the year. It should be built at a location where the height of the river is sufficient to get the maximum possible potential energy from water.