A rock is suspended by a light string. When the rock is in air, the tension in the string is 39.2 N. When the rock is totally immersed in water, the tension is 28.4 N. When the rock is totally immersed in an unknown liquid, the tension is 18.6 N. What is the Density of the unknown liquid. - When I looked at this problem, I though we needed to know the volume of the rock. Can someone show me how to do it without the volume of this rock?

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Physics

7 November, 21:21

A rock is suspended by a light string. When the rock is in air, the tension in the string is 39.2 N. When the rock is totally immersed in water, the tension is 28.4 N. When the rock is totally immersed in an unknown liquid, the tension is 18.6 N. What is the Density of the unknown liquid. - When I looked at this problem, I though we needed to know the volume of the rock. Can someone show me how to do it without the volume of this rock?

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Kadin Dougherty · Answer 1

1.1 g/cm^3

Explanation:

weight in air, Wa = 39.2 N

weight in water, Ww = 28.4 N

weight in liquid, Wl = 18.6 N

Let d be the density of unknown liquid.

By using the formula of relative density

relative density of unknown liquid

= (wt. in air - wt. in water) / (wt. in water - wt. in liquid)

d = (Wa - Ww) / (Ww - Wl)

d = (39.2 - 28.4) / (28.4 - 18.6)

d = 10.8 / 9.8

d = 1.1

Thus, the density of unknown liquid is 1.1 g/cm^3.