Physics Force and pressure

Question

Suppose you balance a 2.8-kgkg ball on the tip of your finger, which has an area of 1.0 cm2cm2 . What is the pressure on your finger?

Answer 1

Pressure is defined as the force per unit area, P = F/A.

The mass of the 2.8 kg ball must be converted to force using F = ma = 2.8 kg x 9.8 m/s^2 = 27.4 N.

As the area is 1 cm^2, it is equivalent to 0.0001 m^2. So to express the pressure in mks units (N/m^2), we should use P = 27.4 / 0.0001 m^2 = 2.74 x 10^5 N/m^2. If the answer should be given in N/cm^2, the answer would then be 27.4 N/cm^2. I hope this helps.