In a classroom demonstration, a 79.2-kg physics professor lies on a “bed of nails.” The bed consists of a large number of evenly spaced, relatively sharp nails mounted in a board so that the points extend vertically outward from the board. While the professor is lying down, approximately 1950 nails make contact with his body.

Question

In a classroom demonstration, a 79.2-kg physics professor lies on a “bed of nails.” The bed consists of a large number of evenly spaced, relatively sharp nails mounted in a board so that the points extend vertically outward from the board. While the professor is lying down, approximately 1950 nails make contact with his body.
a) What is the average force exerted by each nail on the professor's body?
b) If the area of contact at the head of each nail is 1.26 × 10^–6 m2, what is the average pressure at each contact?
a) 79.2*9.8/1950= 0.398N
Just need help with b.

Tom · Accepted Answer

so 0.398/1.26 × 10^–6 m2=3.16x10^-7Pa

Damon · Answer

divide the force on each nail by the area of the nail head to get Newtons per square meter or Pascals of pressure.