# Finding the coefficient of friction

• xSnoopy
In summary, the conversation discusses a problem involving finding the resultant force on two blocks at different angles. The participants discuss using equations to solve for the force and acceleration, and eventually finding the value of μ.
Well on the horizontal block, what are the forces acting?

On the vertical block, what are the forces acting?

Find the resultant force on each block. What do you get?

Well its not at equilibrium so i can't just sum the forces to get zero ...?

xSnoopy said:
Well its not at equilibrium so i can't just sum the forces to get zero ...?

That is why you put the resultant force as 'ma'

so Force normal = 2.94N
and force moving horizontal would be (0.3)(a)

then
μ(2.94) + (0.3)(a) = (0.3)(a) ? ... crap I'm not getting something here :/

xSnoopy said:
so Force normal = 2.94N
and force moving horizontal would be (0.3)(a)

then
μ(2.94) + (0.3)(a) = (0.3)(a) ? ... crap I'm not getting something here :/

Consider the horizontal and vertical blocks separately.

On the horizontal block you have a tension T

so T-μ(0.3*9.81) = 0.3a

now do the same for the vertical block.

You will now have two equations in T and a. Eliminate 'T' from the two, leaving one equation in 'a'.

Oh like net force?

The vertical would then be..

T - 0.3a = 0.3a ?

xSnoopy said:
Oh like net force?

The vertical would then be..

T - 0.3a = 0.3a ?

Vertically, you'd get mg-T, since the block moves down.

So you would get

T-μ(0.3*9.81) = 0.3a
(0.3*9.81) - T = 0.3a

and substitute ?..

T-μ(0.3*9.81) = (0.3*9.81) - T

that doesn't cancel out the T's ?

xSnoopy said:
So you would get

T-μ(0.3*9.81) = 0.3a
(0.3*9.81) - T = 0.3a

and substitute ?..

T-μ(0.3*9.81) = (0.3*9.81) - T

that doesn't cancel out the T's ?

No. If you add the two equations together, what do you get?

You get

μ(2.94) + (2.94) = 0.6a ?

right, so you can find 'a' in terms of 'μ'. You also know that 'a' is constant. Now use a kinematic equation involving distance, time and acceleration.

You should now be able to get the value of μ.

## What is the coefficient of friction?

The coefficient of friction is a measure of the amount of resistance between two surfaces in contact with each other. It represents the ratio of the force required to move one surface over the other to the normal force between the two surfaces.

## Why is it important to find the coefficient of friction?

The coefficient of friction is an important factor in understanding the behavior and performance of objects in contact with each other. It is used to predict the force required to move an object, as well as to determine the amount of energy lost due to friction.

## How do you calculate the coefficient of friction?

The coefficient of friction can be calculated by dividing the force required to move an object by the normal force between the two surfaces. It can also be determined experimentally by measuring the angle at which an object begins to slide down an inclined plane.

## What factors affect the coefficient of friction?

The coefficient of friction can be affected by several factors, including the nature of the surfaces in contact, the roughness of the surfaces, the amount of force applied, and the presence of any lubricants or contaminants.

## Can the coefficient of friction be negative?

No, the coefficient of friction cannot be negative. It is always a positive value, representing the amount of force required to overcome the resistance between two surfaces. However, it can have a value of zero in cases where there is no resistance between the surfaces, such as in the case of a lubricated surface.

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