Q. 9

Find the relative density of wood. Explain the process.

Answer :

Relative density is also called specific gravity of a solid .Relative density can be determined using Archimedes principle.

Arccoding to Archimedes principle ,when a body is wholly or partially immersed in a fluid ,it experience an upward thrust equal to the weight of the fluid displaced. Archimedes principal can be utilised to determine the relative density of solid substance that does not dissolve in water.

As given in the figure first we measured the weight of the object in air which is given in A , then we put the system in the water vessel the weight the object in water(B) Is noted .As we put our system in the water vessel some amount of liquid will comes out from the vessel, which is collected in C . Now we can easily measure the weight of water in C. The data are following -

A is a real weight (weight of an object in air) = W1

B is apparent weight (weight of an object in fluid) = W2

C is apparent loss of weight (weight of fluid displaced) = W1-W2

Measuring the weight of displaced fluid is equal to apparent loss of weight; this apparent loss is the buoyancy force on an object which is upthrust.

Apparent loss of weight is equal to the weight of displaced fluid.

Real weight = apparent weight + apparent loss

Since apparent loss is equal to upthrust

Real weight = apparent weight + upthrust

Upthrust =real weight – apparent weight.

Now we can find the relative density of the substance ,which tells us how much the substance is denser then water.

The formula for relative density is-

The relative density

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