Tag: fluid pressure

Questions Related to fluid pressure

A piece of ice is floating in a beaker containing thick sugar solution of water. As the ice melts, the total level of the liquid:

archimedes' principle fluid pressure properties of matter physics

  1. increases

  2. decreases

  3. remains unchanged

  4. insufficient data

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Correct Option: A
Explanation:

Let $\rho $=density of sugar solution $> \rho _{w}$
m=mass of ice.
In floating condition weight=upthrust
$\therefore $   $mg=V _{I}\rho g$
or $\displaystyle V _{I}=\frac{m}{\rho }$          (i)
When ice melts, m mass of ice becomes m mass of water. Volume of this water formed.
$\displaystyle V _{F}=\frac{m}{\rho _{w}}$          (ii)
Since $\rho _{w}< \rho $, $V _{F}> V _{I}$. Hence level will increase.

A boat full of scrap iron is floating on water in a lake. If all the iron is dropped into the water, the level of water will:

archimedes' principle fluid pressure properties of matter physics

  1. go up

  2. fall down

  3. remain the same

  4. Can not be decided.

Show answer
Correct Option: B
Explanation:
According to Archimedes' principle, any body completely or partially submerged in a fluid at rest is acted upon by an upward, or buoyant force,the magnitude of which is equal to the weight of the fluid displaced by the body
As boat filled with scrap iron is floating on lake, buoyant force acting on boat is more than its weight.
                                              $F _b > W _b + W _{fe}$
since,                                    $W _b<W _b +W _{fe}$
therefore,level of water will fall down across the boat.

If a piece of wood just floats in water. What happens to it in ethanol?

archimedes' principle fluid pressure properties of matter physics

  1. It floats higher

  2. It stays as before

  3. It sinks

  4. First sinks and then rises

Show answer
Correct Option: C
Explanation:

At room temperature and standard pressure, the first family of alcohol (methanol, ETHANOL and iso-propyl) all have densities of about 0.79g/cc compare to water at the same conditions with a density of 1.0g/cc.

Since the density of ethanol is less than the density of water so, when a piece of wood which is just floating in water is placed in ethanol, sinks.

Which of the following instrument is used to measure the volume of a solid by water displacement ?

archimedes' principle fluid pressure properties of matter physics

  1. Thermometer

  2. Graduated cylinder

  3. Buret

  4. Salt bridge

  5. Conductivity tester

Show answer
Correct Option: B
Explanation:

Graduated cylinder  is used to measure the volume of a solid by water displacement. The volume of water displaced will be equal to the volume of the solid.

A boat is floating on the surface of water in a tank carrying steel balls. If the balls are thrown into the tank one by one, how will it affect the level of water?

archimedes' principle fluid pressure properties of matter physics

  1. It will rise

  2. It will fall

  3. It will remain unchanged

  4. First it will rise and then fall

Show answer
Correct Option: B

A dog is sitting in a boat which is floating in a pond. If the dog drinks some water from the pond then:

archimedes' principle fluid pressure properties of matter physics

  1. the level of water in the pond decreases

  2. the level of water in the pond increases

  3. the level of water in the pond first increases, then decreases

  4. the level of water in the pond remains unchanged

Show answer
Correct Option: D
Explanation:

There Will be no change in the water level of the pond, as the water which was drawn from the pond went to the man's body, thereby increasing his weight. So the decrease in level of water will be compensated by volume displaced by increase in weight of the man.

Therefore option $D$ is correct.

A vessel completely filled with water is weighed. This vessel will weigh ________ after a wooden block is gently moved into the water until it stays in equilibrium while any displaced water is removed.

archimedes' principle fluid pressure properties of matter physics

  1. More

  2. Same

  3. Less

  4. None of the above

Show answer
Correct Option: B
Explanation:

False because the liquid displaced has the same weight as the wooden block has The weight of the displaced liquid from the vessel is same as the weight of the wooden block.
Hence,  the weight will remain the same.

A sphere is floating in water its $\dfrac{1}3rd$ part is outside the water and when the sphere is floating in unknown liquid, it's $\dfrac {3}{4}th$ part is outside the liquid than the density of the liquid is

archimedes' principle fluid pressure properties of matter physics

  1. $\dfrac{4}9\ gm/cc$

  2. $\dfrac{9}4\ gm/cc$

  3. $\dfrac{8}3\ gm/cc$

  4. $\dfrac{3}8\ gm/cc$

Show answer
Correct Option: C
Explanation:

volume of liquid inside the liquid1=2/3rd of total volume

volume of liquid inside the liquid2 = 1/4th of total volume

density of liquid= (2/3)/(1/4) = 8/3 g/cc

A boat carrying steel balls is floating on the surface of water in a tank.If the balls are thrown into the tank one by one , how will it affect the level of water :

archimedes' principle fluid pressure properties of matter physics

  1. It will remain unchanged

  2. It will rise

  3. It will fall

  4. First it will raise and then fall

Show answer
Correct Option: A
Explanation:

Since the weight remains constant & so does buoyant force on a floating body. Hence there will be no change in level of water.

Choose the correct statement from the following:

archimedes' principle fluid pressure properties of matter physics

  1. A body will sink in a liquid if its weight is equal to or greater than the weight of the liquid displaced by it

  2. A body will float in a liquid if its weight is equal to or less then the weight of liquid displaced by it

  3. When a body floats in a liquid, the portion of the body above the surface of the liquid is independent of the density of the body relative to that of the liquid

  4. In still air, a hydrogen filled balloon rises up to certain height and then stops rising.

Show answer
Correct Option: B,D
Explanation:
According to Archimedes
${ F } _{ b }=$weight of liquid displaced by object
The object floats if ${ F } _{ b }\ge mg$
Weight of liquid displace$\ge $ weight of object
When a body floats the portion immersed or above liquid is dependent on body's density.
The balloon rises till ${ F } _{ b }> mg$. Then stops, since ${ F } _{ b }$ decreases as air gets thin.