Question

In: Physics

A rock is suspended by a light string. When the rock is in air, the tension...

A rock is suspended by a light string. When the rock is in air, the tension in the string is 52.9 N . When the rock is totally immersed in water, the tension is 32.6 N . When the rock is totally immersed in an unknown liquid, the tension is 14.4 N .

What is the density of the unknown liquid?

Solutions

Expert Solution

Gravitational acceleration = g = 9.81 m/s2

Density of water = 1 = 1000 kg/m3

Density of the unknown liquid = 2

Weight of the rock = Tension in the string when the rock is air = W = 52.9 N

Volume of the rock = V

Buoyant force on the rock when immersed in water = F1 = 1Vg

Tension in the string when the rock is immersed in water = T1 = 32.6 N

When the rock is immersed in water the tension in the string and the buoyant force on it supports the weight of the rock.

W = F1 + T1

W = 1Vg + T1

52.9 = (1000)(9.81)V + 32.6

V = 2.0693 x 10-3 m3

Buoyant force on the rock when it is immersed in the unknown liquid = F2 = 2Vg

Tension in the string when the rock is immersed in unknown liquid = T2 = 14.4 N

When the rock is immersed in the unknown liquid the tension in the string and the buoyant force on it supports the weight of the rock.

W = F2 + T2

W = 2Vg + T2

52.9 = 2(2.0693x10-3)(9.81) + 14.4

2 = 1896.56 kg/m3

Density of the unknown liquid = 1896.56 kg/m3


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