Question

A block of brass of mass $0.5kg$ and density $8\times {10}^{3}kg/m^3$ is suspended from a string. What will be the tension in the string if the block is completely immersed in water? $(g=10m/s^2)$

Answer 1

R.E.F image

mass m = 0.5 kg

density $d=8\times {10}^{3}kg/m^3$

$\Rightarrow$ volume $v=\frac{m}{d}=\frac{0.5kg}{8000kg/m^3}=6.25\times {10}^{-5}{m}^3$

after fell immersed water dispersed

will be $v=6.25\times {10}^{-5}{m}^3$

$\Rightarrow$ upthrust force $=F=pvg={10}^3\times 6.25\times {10}^{-5}\times 10$ Newton

f = 0.625 Newton

F.B.D of block

rest $\Rightarrow$ Net force = 0

$\Rightarrow T+F-mg=0$

$\Rightarrow T=mg-f=0.5\times 10-0.625=+.375N$