Question

A rock weighs 1400 N in air, has an apparent weight of 900 N when submerged in fresh water (998kg/m^3).The volume in m^3 of the rock is (g = 9.8 m / s2 )

Answer 1

According to given data

weigh in air = 1400 N

Apparent weigh = 900 N

Density = 998 Kg/m³

Solution

Now,according to formula :

Loss of water displaced = loss of weight

1400-900 = V x 998 x 9.8

500 = 9780.4 x V

900 = 1400 - V x 998 x 9.8

9780.4 V =  500

                V  = 500/9780.4

                 V = 0.0051 m³

Answer 2

Loss of weight= 1400-900=500N

Density p=998kg/m3

Loss of weight=Loss of water displaced

500=pVg

V= 0.05m3

The questions are very tricky hence special attention should be paid to the numbers in the questions.

Always try to attempt this questions from top to bottom format as it becomes easier to solve.

Summarize the formula so that you don't have to depend on the answers only.