A book and a copy are placed on the table.

Question

A book and a copy are placed on the table. The pressure is same on the table. The masses of the book and copy are 0.4kg and 0.75kg respectively. If the area covered by the copy is 2.25m^2, then area covered by the book will be?

Answer 1

This is a simple question demonstrating the relationship between Pressure, Force and Area.

The pressure exerted = the total force/total area. Or P=F/A

The total force exerted = mass*acceleration. In this case, the acceleration is due to gravity so F = mg

 

You are given:

2 Masses- Mass of book = 0.4kg and mass of copy = 0.75kg. Using the equation F=mg the downward force exerted by the:

Book = F = 0.4kg*9.81m/s² = 3.924kg*m/s². Or 3.924 Newtons. (Bear in mind 1 Newton = 1kg*m/s2)

Copy = F = 0.75kg*9.81m/s2 = 7.3575kg*m/s2. Or 7.3575 Newtons.

This gives us our values for Force.

 

You are told that the area the copy takes up is 2.25m². This gives us our value for Area of the Copy.

We now have both the Force and Area of the copy. We can now find Pressure. P = F/A or 7.3575 N/2.25m² = 3.27N/m².

 

 

You are told that both exert the same amount of pressure on the table. Therefore the P of the Book is also 3.27N/m².

 

We now have the Pressure and Force of the Book. We can now find Area. P = F/A or 3.27N/m² = 3.924 N/A

A is our unknown. Multiply both sides by A, then divide by 3.27N/m² gives A = 3.924 N/3.27N/m² = 1.2m²

 

Therefore the total area covered by the book is: 1.2m².