Question

If a block of relative density 0.4 is submerged inside water and it is attached to bottom of container by a string. If mass of the block is 2 kg then the tension in string is T Newton. Find (g = 10m/s2)​

Answer 1

Answer:

Correct option is

D

20N

as seen from diagram, we have

T+mg=Fb

⇒T=Fb−mg

⇒T=Vρwaterg−mg   where V=volume of water displaced= volume of wooden block

⇒T=ρwoodmρwaterg−mg

⇒T=kρwatermρwaterg−mg

⇒T=mg(k1−1)=8×10(0.81−1)=20

Answer 2

Answer:

The answer to this question is:4000N.

Explanation:

The tension in the string, T, can be calculated using the concept of buoyancy force. The buoyancy force is the force exerted on an object when it is submerged in a fluid. This force acts in an upward direction and is equal to the weight of the fluid displaced by the object.

Since the block has a relative density of 0.4, the fraction of its volume that is submerged in the water is 0.4. Therefore, the volume of the water displaced by the block is 0.4 times the volume of the block. The weight of the water displaced is given by the product of its volume and the acceleration due to gravity (g).

Hence, the buoyant force can be expressed as:

$Fbuoyancy = ρwater * g * Vdisplaced$

Since the block is in equilibrium, the net force acting on it must be zero. Hence, the tension in the string must be equal to the buoyant force:

$T = Fbuoyancy = ρwater * g * Vdisplaced$

Finally, we can calculate the tension in the string by substituting the values for the density of water (ρ_water = 1000 kg/m^3), the acceleration due to gravity (g = 10 m/s^2), and the volume of the water displaced ($Vdisplaced = 0.4 * block volume$).

$T = 1000 * 10 * 0.4 * (block volume) = 4000 N$

So the tension in the string is 4000 N.

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