Question

# A scale from which a rock is suspended reads 5 N when the rock is out of water and 3 N when the rock is submerged. The density of the rock is A) the density of water. B) 1.5 times the density of water. C) 2.5 times the density of water. D) 3.5 times the density of water. E) none of the above

Answer

B) 1.5 times the density of water.

- Find the weight of the displaced water. Note that the difference between the two scale readings is equal to the weight of the water displaced by the rock.
- Divide the weight of the rock by the weight of the displaced water. This will give you the specific gravity of the rock.
- Compare the specific gravity of the rock to the specific gravity of water, which is 1. If the specific gravity of the rock is greater than 1, the rock is denser than water. If it is less than 1, the rock is less dense than water.