it refers to the inverse of the force between two point charges separated through unit distance.
1/2 of 4 pies is 2 pies.
The surface area of the 'sphere' is four times the area of a 'great circle',or (4 pi) times the RADIUS squared.
because it is negligible, in other words it is too small for our body's to senseThe formula to find the force between 2 objects is F = G x(m1 m2)/r^2where G is a constant of 6.67 x 10^-11r being the distance between the 2 objectsand m1 and m2 being mass of both objects respectively.as G is a very very small number one or both objects have to be of considerably large mass in order to feel any force between them, in your case since leg of your chair and you and small masses, the force would be less than than enough to be felt.