An object weighs 10N in air and 70N in water. What is it's weight when immersed in a liquid of relative density 1.5?

5.5 N

Explanation:

We are given;

Real weight of an object in air as 10 N Apparent weight in water as 7 N Relative density of a liquid is 1.5

We need to calculate the apparent weight when in liquid.

First we calculate upthrust

Upthrust = Real weight - Apparent weight

= 10 N - 7 N

= 3 N

Then calculate the upthrust in the liquid.

we need to know that;

Relative density of a liquid = Upthrust in liquid/Upthrust in water

Therefore;

1.5 = U : 3 N

Upthrust in liquid = 3 N * 1.5

= 4.5 N

Therefore, the upthrust of the object in the liquid is 4.5 N

But, Upthrust = Real weight - Apparent weight

Therefore;

Apparent weight in Liquid = Real weight - Upthrust

= 10 N - 4.5 N

= 5.5 N

Thus, the weight when the object is immersed in the liquid is 5.5 N