Question

How could you find the density of an irregular object which floats in water?

Answer 1

We know that density `rho="Mass"/"Volume"=m/V_"o"` ....(1)

One of the methods to find volume of an irregular shaped object is with the help of water displacement method. Method becomes complicated if the objects floats.

For such an object we use the sinker method. A sinker is a weight tied to the floating object to hold it down and submerge it completely in graduated container. Following steps will help to find the density `rho` of the object.

1. Find mass `m` of the object with the help of a Physical balance and record it.
2. Pour water in to the graduated container about one third of its depth and record the volume of water `V_w`
3. Tie the sinker with a thread and lower it gently in the container without splashing. Record the new volume `V_1`.
4. Attach the sinker to the object with a thread and lower both in the container gently, without splashing. Record the new volume `V_2`

Volume of sinker`=V_1-V_w`
Volume of sinker and object `=V_2-V_w`
`:.` Volume of object `V_"o"=(V_2-V_w)-(V_1-V_w)=V_2-V_1`

Calculate `rho` with equation (1).