- #1

Tepictoc

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## Homework Statement

I have a box on a horizontal plane.

Given data: mass = 0.25kg

height of object = 14 cm

width of object = 9cm

Calculate the coefficient of static friction.

## Homework Equations

μs = Ff/N (N is the normalforce)

F = Ff = μ*N

mg = 2.45 Newton

## The Attempt at a Solution

I apply an unknown force on the object from the left side at the height of x to see where it starts to tip over instead of slide. Looks like it's at 13 cm. x = 13

The vertical forces:

N cancels out mg since the object is not accelerating up or down, so N=mg.

μk is irrelevant in this case so I'll just write μ when I mean μs.

The horizontal forces:

Ff is acting in the opposite direction of the applied Force

F = Ff = μ*N

L is the length to the middle 4.5cm

mg*L - F*x = 0

I substitute in μ*mg instead where F*x is

mg*L - μ*mg = 0

This is where I think I might be going wrong:

μ = mg*L/mg

μ = L

Which would mean the coefficient of static friction is 4.5 or 0.45 which is too high.

When I angle (at 12 degrees) the same object on the same surface and calculate the μs it became 0.21

If I go this way it's slightly better but probably wrong since one m disappears:

μ = mg*L/g = 0.24