Tag: physics

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Questions Related to physics

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.

Multiple choice fluid dynamics option b: engineering physics physics

Hot syrup flows faster because:

  1. Surface tension increases when temperature is increased.

  2. Viscosity decreases when temperature is increased.

  3. Viscosity increases when temperature is increased.

  4. Surface tension decreases when temperature is increased.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Hot syrup is liquid at higher temperature. We know that as temperature increases viscosity decreases for liquids. So, hot syrup flows faster as viscosity decreases.

Multiple choice fluid dynamics option b: engineering physics physics

Assertion : Water flows faster than honey.
Reason: The coefficient of viscosity of water is less than honey.

  1. Both assertion and reason are true and reason is correct explanation of assertion.

  2. Both assertion and reason are true but reason is not the correct explanation of assertion.

  3. Assertion is true but reason is false.

  4. Both assertion and reason are false.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Velocity is inversely proportional to coefficient of viscosity, $\eta$ of water is less than that of honey.
Hence, water flows faster than honey.

Multiple choice fluid dynamics option b: engineering physics physics

With increase in temperature, the viscosity of:

  1. gases decreases and liquid increases

  2. gases increases and liquid decreases

  3. both gases and liquid increases

  4. both gases and liquid decreases
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The viscosity of liquid is inversely proporional to the square of the temperature, therefore as we increase the temperature, the viscosity of liquids will decrease.


Similarly, the viscosity of gases is linearly proportional to the temperature. hence as the temperature increases, the viscosity will increase

Multiple choice fluid dynamics option b: engineering physics physics

A spaceship entering the earth's atmosphere is likely to catch fire. This is due to:

  1. The surface tension of air

  2. Air Friction

  3. The high temperature of upper atmosphere

  4. The greater portion of oxygen in the atmosphere at greater height.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

As the body enters Earth's atmosphere, it falls at very high speeds. This high speeds cause a lot of friction with the air, causing the parts to catch fire.
Option B.

Multiple choice fluid dynamics option b: engineering physics physics

When an object is dropped into a fluid, the extent of splash, due to buoyant force of fluid, depends on:

  1. sliding friction

  2. rolling friction

  3. fluid friction

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

The splash, due to buoyant force of a fluid depends on fluid friction.