Question

. A piece of iron of
density 7.8 × 103kg/m3 and volume 100 cm3 is totally
immersed in water. Calculate (a) the weight of the iron piece in air (b) the
upthrust and (c) apparent weight in water. (ans. (a) 7.8N (b) 1N (c) 6.8 N)

Answer 1

density of iron (Dr) = 7.8×10³ kg/m³
volume of iron piece(V) = 100cm³ = 10^(-4) m³
density of water (Dw) = 10³ kg/m³

(a) weight in air = Dr×V×g = 7.8×10³ × 10^(-4) ×10 = 7.8 N

(b) upthrust is the buoyant force exerted by water
    upthrust = Dw×V×g = 10³ × 10^(-4) ×10 = 1N

(c) apparent weight in water = weight in air - upthrust
                                         = 7.8N - 1N = 6.8N

Answer 2

hope it will help you.......