The component of weight(mg) that is responsible for the motion of boxes on ramp is:
Where m = mass of the boxes.
g = Acceleration due to gravity = 9.8
= The angle the ramp makes with the ground. In this case it is 30°.
Since the frictional force is:
μ*N.
Where,
μ = Frictional Coefficient
N = Normal to the ramp =
Therefore, the frictional force becomes =
= μ*
Apply Newton's second law we would get:
- μ* = 
=>
=
μ 
-- (A)
Now according to equation of motion:
Where x = 5.8m
= 0
= 0
= 10.24
Plug in the value in the above equation you would get:
= 1.1328
Plug in in equation (A) and solve for μ, you would get,
μ = 0.4439
Where m = mass of the boxes.
g = Acceleration due to gravity = 9.8
Since the frictional force is:
Where,
μ = Frictional Coefficient
N = Normal to the ramp =
Therefore, the frictional force becomes =
Apply Newton's second law we would get:
=>
Now according to equation of motion:
Where x = 5.8m
Plug in the value in the above equation you would get:
Plug in
μ = 0.4439