A piece of iron of density `7.8 xx 10^(3) kgm^(-3)` and volume `10^(-4) m^(3)` is fully immersed in water. Calculate (i) weight of the iron piece in air (ii) upthrust of water on the iron piece (iii) apparent weight of the iron piece in water. Given `g=10ms^(-2)`

Explanation

Given `rho=7.8 xx 10^(3)kgm^(3), V=10^(-4)m^(3)`.
(i) Weight of iron air `=(rhoV)_(g)=7.8 xx 10^(3) xx 10^(-4) xx 10^(t)=7.8 N`
(ii) Upthrust of water on iron piece `=(V)rhowg=10^(-4) xx 10^(3) xx 10^(1)=1N`
(iii) Apparent weight of iron piece in water `=(i) -(ii) =7.8 -1.0=6.8N`