Tag: when do objects float on water?

Questions Related to when do objects float on water?

Give reasons as to why It is easier to swim in sea water than in river water. 

  1. The density of river water is greater

  2. The density of sea water is greater

  3. Both their densities are the same

  4. None of these


Correct Option: B
Explanation:

Sea water contains dissolved salts which makes its density more than river water Hence upthrust is more in sea water than river water So it is easier to swim in sea water than in river water 

Give reasons as to why bodies like cork or wood float in water.

  1. They are denser than water

  2. They are less dense than water

  3. They have the same density as that of water

  4. None of these


Correct Option: B
Explanation:

Density of cork or wood are less than that of water hence they float in water

Give reasons as to why bodies like stones and metals sink in water.

  1. They have higher density compared to water

  2. They have lesser density compared to water

  3. They have the same density as that of water

  4. None of these


Correct Option: A
Explanation:

Bodies like stones ans metals sink in water as these substances have density more than that of water

A hot air balloon rises because it is filled with a gas :

  1. denser than air

  2. less dense than air

  3. as dense as air

  4. the given statement is wrong


Correct Option: B
Explanation:

More denser objects stays at the bottom.

Since, the hot air balloon rises because it is filled with a gas which is less dense than the air .So, the air has the tendency to move down and the balloon has the tendency to move in the upward direction.

What happens when an object having density less than that of water is immersed in it?

  1. It sinks

  2. It floats

  3. Unsure

  4. May sink or float


Correct Option: B
Explanation:

the buoyant force depends on the density of liquid. When the density of the object is less than that of the liquid, it floats on the liquid because the upthrust or buoyant force of water is more than the gravity acting on the object.

If the weight of the body immersed in the liquid is equal to the force of buoyancy acting on it, then the body will

  1. Float above the liquid surface

  2. Float just inside the liquid surface.

  3. Sink

  4. None


Correct Option: B
Explanation:

If the weight of the body immersed in the liquid is equal to the force of buoyancy acting on it, then the body will float just inside the liquid surface.

A piece of ice is floating in a jar containing water. When ice melts, the temperature of water falls from $4^0C$ to $1^0C$. The level of water :

  1. rises

  2. falls

  3. remains unchanged

  4. changes erratically


Correct Option: C
Explanation:

Remains unchanged because there is no change in mass.

The correct option is C.

A steel wire of length 1 m and cross-sectional area $1.5 mm^2$ is hung from. rigid support, with a stone of volume 2000 cm^3 hanging from the other end. Find the decrease in the length of the wire, when the stone is completely immersed in water. (Ysteel = $210^11 Nm^-2$, $\rho$ water = $103 kgm^-3$)

  1. 0.06533 mm

  2. 0.02533 mm

  3. 0.04533 mm

  4. 0.011533 mm


Correct Option: C

A cubical block of iron of side $5cm$ is floating in mercury taken in a vessel. What is the height of the block above mercury level. $(\rho _{Hg}=13.6g/cm^3 ,\rho _{fe}=7.2 g/cm^3)$

  1. $3.65cm$

  2. $3.35cm$

  3. $2.65cm$

  4. $2.35cm$


Correct Option: C

An ice berg is floating in sea water. The density of ice is $ 0.92\, gm\,cm^{-3}$ and that of sea water is $ 1.03\,gm\,cm^{-3}$. The  percentage of ice berg below surface of water is 

  1. 3 %

  2. 11 %

  3. 89 %

  4. 92 %


Correct Option: B