Question

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?​

Answer 1

Answer:

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