Tag: option b: engineering physics

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Questions Related to option b: engineering physics

Multiple choice fluid dynamics option b: engineering physics physics

Choose the wrong statement.

  1. Viscous force always supports the motion.

  2. A denser fluid always more viscous than a less dense fluid.

  3. Any object cannot have a velocity after a sufficient long time more than its terminal velocity in a given fluid.

  4. If a body is at rest in a fluid then the viscous force on it is zero.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Viscous force is a frictional force which opposes the relative motion between liquid molecules. Terminal velocity is the velocity attained by the particle when net force on it becomes zero the body cannot have more velocity than terminal velocity in respective fluid.

Multiple choice fluid dynamics option b: engineering physics physics

The velocity of falling rain drops attains limited value because of :

  1. surface tension

  2. upthrust due to air

  3. viscous force exerted by air

  4. air current
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Gravity does cause things to fall with increasing speed, but as they speed up viscous force by air increases increases. Since according to stokes law $F _r \propto v$.  Eventually the acceleration stops and the raindrop reaches a constant terminal velocity.

Multiple choice fluid dynamics option b: engineering physics physics

The quality of fountain-pen ink depends largely on:

  1. Surface tension of the liquid

  2. Viscosity of ink

  3. impurities in ink

  4. Density of ink
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The quality of fountain-pen ink depends largely on viscosity of ink because as the viscosity of ink is more, it requires hard pressure on the pen to write and as the viscosity of ink is less  we can write smoothly.

Multiple choice fluid dynamics option b: engineering physics physics

Two identical lead shots are dropped at the same time in two glass jars containing water and glycerine. The lead shot dropped in glycerine descends slowly because:

  1. Viscous force is more in water than in glycerine

  2. Viscous force is more in glycerine than in water

  3. Surface tension is more in water

  4. Surface tension is more in glycerine
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Glycerine viscosity is 950 cP and water viscosity is 0.89 cP. We can see that glycerine has high viscosity. High viscous force of glycerine increases the time of drop of lead shot than in water.

Multiple choice fluid dynamics option b: engineering physics physics

After the storm, the sea water waves subside due to:

  1. Surface tension of sea-water

  2. Disapperance of heavy currents

  3. The viscosity of sea water

  4. Gravitational pull of the storm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

After the storm, the sea water waves subside due to the viscosity of sea water. Since viscosity's main cause is cohesive force which acts in intermolecular particles. So, sea water waves subside due to these cohesive force between water molecules.

Multiple choice fluid dynamics option b: engineering physics physics

A good lubricant must have:

  1. high viscosity

  2. low viscosity

  3. high density

  4. low surface tension
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Good lubricant must have high viscosity. So, that machine parts can do work better. Higher the viscosity of the lubricants the greater is its ability to provide boundary lubrication, which means a boundary between moving parts. 

Multiple choice fluid dynamics option b: engineering physics physics

When stirring of a liquid is stopped, the liquid comes to rest due to:

  1. surface tension

  2. gravity

  3. viscosity

  4. buoyancy
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When stirring of a liquid is stopped, the liquid comes to rest due to viscosity of liquid. While stirring fluid at the axis moves faster in circular path whereas the fluid in contact with the walls does not move. So, the viscous drag force acting between the fluid layers tries to restrict the relative motion of them. So, by viscous drag force liquid comes to rest. 

Multiple choice fluid dynamics option b: engineering physics physics

Coefficient of viscosity of a gas:

  1. increases with increase of temperature.

  2. decreases with increase of temperature.

  3. remains constant with increase of temperature.

  4. may increase or decrease with increase of temperature.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

With increase in temperature, the molecule of gas carry more momentum and collide more often, that means more viscosity. So, coefficient of viscosity of a gas increases  with increase of temperature.

Multiple choice fluid dynamics option b: engineering physics physics

Viscosity of water at constant temperature is:

  1. more in deep water

  2. more in shallow waters

  3. less in deep water

  4. same in both deep water and shallow waters
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In deep water temperature decreases, viscosity of water increases with decrease in temperature. So, viscosity of water at constant temperature is more in deep water as temperature is less in deep waters.