The static friction is a friction between two objects that are not moving relative to each other.
The static friction must be overcome by an external applied force before the object can move.
The max static fraction (Fμ) is defined as the product of the coefficient of static friction (μ) and the normal force (Fn).
Fμ=μ*Fn
The normal force is defined as the net force normal to the surface, for one body had been put on a surface with out any external tension, it equal to the gravitational force (equally in value and oppositely in direction).
[tex]F_{n}=F_{g}=mg=4*9.8=39.2N[/tex]
Thus, the max. force of friction will be
Fμ= [tex]0.45 * 39.2 = 17.64N[/tex]
Note that: the object will not be moved until the applied force more than the max. fraction force as we see in our problem.
The value of maximum friction force will be equal to 17.658 N.
To find the normal force that is been applied to the box, equate all the vertical forces that will act on the box,
N = m x g
N = 39.24 N
We know that the friction force that will be applied on the box can be given as,
[tex]F = \mu \times N\\\\F = 0.45 \times 39.24\\\\F = 17.658\rm\ N[/tex]
Thus, the value of maximum friction force will be equal to 17.658 N.
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