Question

A cubical block of wood weighing 200 g has a lead piece fastened underneath. Find the mass of the lead piece which will just alow the block of float in water. Specific gravity of wood is 0.8 and that of lead is 11.3.

Answer 1

Correct Answer - D
`rho_w=0.8gm/cc`
=density of wood
`rho_(pb)=11.3gm/cc`
=density of lead
`m_w=200g`
`=mass of good

`Here (m_2m_(pb))g=(V_w+V_(pb))rhoxxg`
[where rho=density of water]
`rarr (m_w+m_(pb))=(m_2/rho_w+m_(pb)/rho_(pb))rho`
`rarr (200+m_(pb))=(200/0.8+m_(pb)/11.3)xx1`
`-m_(pb)-m_(pb)/11.3 =250-200`
`rarr (10.3_(pb)/11.3=50`
`-. m_(pb)=(50xx11.3)/10.3=54.8gm