Tag: physics

Questions Related to physics

Which of the following quantity is expressed as force per unit area?

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

  1. Work

  2. Pressure

  3. Volume

  4. Area

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Correct Option: B
Explanation:

Pressure is expressed as force per unit area

Pressure is vector quantity .State true or false.

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

  1. True

  2. False

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Correct Option: B
Explanation:

Pressure is a scalar quantity, not a vector quantity. It has a magnitude but no direction associated with it. Pressure acts in all directions at a point inside a gas. At the surface of a gas, the pressure force acts perpendicular to the surface.

For example. one that does not appear to move or flow. While the gas as a whole does not appear to move, the individual molecules of the gas, which we cannot see, are in constant random motion. Because we are dealing with a nearly infinite number of molecules and because the motion of the individual molecules is random in every direction, we do not detect any motion. If we enclose the gas within a container, we detect a pressure in the gas from the molecules colliding with the walls of our container. We can put the walls of our container anywhere inside the gas, and the force per area (the pressure) is the same. We can shrink the size of our "container" down to an infinitely small point, and the pressure has a single value at that point.

Therefore, it is false. 

Two stretched remembrance of area $2$ and $3\ m^{2}$ are placed in a liquid at the same depth. The ratio of the pressure on them is

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

  1. $1:1$

  2. $2:3$

  3. $\sqrt {2}:\sqrt {3}$

  4. $2^{2}:3^{2}$

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Correct Option: A

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: 

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

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

  2. $p\upsilon ^{2}$

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

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

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Correct Option: A

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

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

  1. True

  2. False

  3. Ambiguous

  4. Data insufficient

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Correct Option: B
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.

We sit in the room with windows open. Then

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

  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

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Correct Option: B
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.

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

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

  1. burning of coal

  2. burning of diesel

  3. flow of water

  4. production of steam

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Correct Option: C
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.


Pascal is a unit used for measuring :

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

  1. buoyant force

  2. thrust

  3. pressure

  4. none of these

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Correct Option: C
Explanation:

Pascal is the S.I. unit of pressure. So, the pressure is measured in the unit pascal.

Pressure acting on a body is a :

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

  1. scalar quantity

  2. vector quantity

  3. slanted force

  4. all the above are wrong

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Correct Option: A
Explanation:

pressure is a scalar quantoty as it does not have any direction.

$1$  millibar is equal to

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

  1. $100 N {m}^{-2}$

  2. $10 N {m}^{-2}$

  3. $1 N {m}^{-2}$

  4. $\displaystyle\frac{1}{100} N {m}^{-2}$

Show answer
Correct Option: A
Explanation:

1 millibar = $10^{-3} bar$

and 1 bar = $10^5$ pa
hence 1 millibar = 100 pa = 100n$m^{-2}$