Question

Question #6a366

Answer 1

see below

Explanation:

there are two kinds of friction:
1) the friction between the body that it is moving and the ground. It can be dry friction (Static or Kinetic) or rolling friction. This friction is influenced by the two materials in contact and by the weight force of the body
2) the friction against the resistance of a fluid (gas or liquid). For air it depends from the relation :

`f= d A Cx v^2`

where A is the face area of the body, Cx is the aerodinamic coefficient, V is the speed of the body (it is the most factor of the resistant force) and d is the density of the fluid that dipends from temperature T, pressure P, umidity (that influences the molecolar mass of air) according to:

`d= (P xx MM)/(RT)`,
R is the universal gases constant