You are working as a letter sorter in a U. S. Post Office. Postal regulations require that employees' footwear must have a minimum coefficient of static friction of 0.5 on a specified tile surface. You are wearing athletic shoes for which you do not know the coefficient of static friction. In order to determine the coefficient, you imagine that there is an emergency and start running across the room. You have a coworker time you, and find that you can begin at rest and move 4.38 m in 1.21 s. If you try to move faster than this, your feet slip. Assuming your acceleration is constant, does your footwear qualify for the postal regulation?

  μ = 0.66,    therefore if it compiesy with the regulations

Explanation:

Let's solve this exercise in part, let's start by finding with kinematics the acceleration of man

           y = v₀ t + ½ a t²

as it starts from rest the initial velocity is zero

          y = ½ a t²

          a =

          a =\frac{2 \ 4.38}{1.21^2}  

          a = 6.46 m / s²

Now let's use Newton's second law,

Axis y

         N- W = 0

         N = W

         N = m g

X axis

on this axis the man exerts a backward force and by the law of action and reaction the floor exerts a forward force of the same magnitude, this forward force is the friction force.

         fr = m a

the friction force has an expression

          fr = my N

let's substitute

      μ mg = m a

      μ = a / g

let's calculate

     μ = 6.46 / 9.8

     μ = 0.66

therefore if you comply with the regulations

the order for strong to weak forces such as

strong nuclear force → electromegnetic force → weak nuclear force → gravitational force

the fundamental forces are those forces that act between to objects or element to make interactions. there are four types of fundamental forces such as strong and weak nuclear forces (due to protons and electrons), electromagnetic force (due to the motion of electrons) and gravitational force (due to orbital movement of the planet). if these forces are arranged on the basis of their maximum strength then the order is

strong nuclear force → electromegnetic force → weak nuclear force → gravitational force

force tends to be low and long diustance masses are high