1. A certain rock has a mass of 20 g and a weight of (0.020)(9.80) N. When compl
ID: 2095825 • Letter: 1
Question
1. A certain rock has a mass of 20 g and a weight of (0.020)(9.80) N. When completely
immersed in water its apparent mass is 15 g and its apparent weight is (0.015)(9.80) N.
a) What is the buoyant force on the rock when it is completely immersed?
b) What is its specific gravity?
2. A piece of wood has a mass of 20 g and when placed in water it floats. That is, if totally
immersed its buoyant force is more than enough to overcome its weight. Therefore a sinker is
attached to the block of wood. Since only the buoyant force of the wood when totally
immersed is required and not that of the wood and sinker combination, first the sinker is
immersed with the wood out of water as in figure 1 to obtain an apparent mass of 40 g. Then
the water in the container is raised to cover the wood as in figure 2 and the apparent mass is 16g
a) What is the buoyant force on the wood when immersed (show calculations)?
b) What is the specific gravity of the wood (show calculations)?
Explanation / Answer
The buoyant force (by definition) is the apparent lost weight when an object (rock in this case) is totally submerged.
In this case the apparent lost weight = (0.005)(9.80) N ANS a)
The b) question should be clarified as to which SG
(ie there are two or rather three substances involved: air, rock, water ???}
Assuming rock's SG is meant, its density compared to water = mass/volume/1000 kg/m
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.