A polythene rod of length 0.5 m floats upright in water.
a) Given that the densities of polythene and water are 920 and 1000 kg/m3 respectively, what is the length of the rod immersed in water?
b) If the rod floats in another liquid with 0.4 m of its length under the liquid surface, what is the density of the liquid?
- 天同Lv 77 years agoFavorite Answer
(a) Let L be the length of rod immersed in water
Upthrust = weight of water displaced = L.A.(1000)g
where A is the cross-sectional area of rod and g is the acceleration due to gravity
Since weight of rod = (0.5A).(920g)
thus, 0.5A.(920g) = LA(1000g)
L = 0.46 m
(b) Using the above equation, but substitute L = 0.4 m and density of water by density of liquid p, we have,
0.5A(920g) = 0.4A(pg)
i.e. p = 1150 kg/m^3