Legend

 Fnet = net force m = mass a = acceleration Fg = force of gravity Ff = force of friction

Interactive Lab

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Coefficient of Friction

 Purpose: Calculate the coefficient of table and masses using simple devices. Material: masses (1 kg, 500 g, 100 g, 50 g) string pulley Setup: Apparatus setup as below diagram.

Background info & calculations:
Since there two masses involved at the same time, we name the mass on the table m1 and the hanging mass m2 .  This way we can distinguish them in the equations.

Ff = Fg = m2g

At the same time.
Ff =
FN = m1g

Therefore:
m2g =
m1g
= m2/m1

However, there is one condition we have to consider, Ff must equal Fg (m2g).  This means that the system must be moving at constant speed, since there's no net force, and in turn no acceleration.

Looking at the forces that acts on the system, we ignored air resistance.  Fg , m1g cancels out with FN and rope tension cancels each other out since they're going in different directions.

 Experiment: Click on the different size masses below to see experiment.

 Calculation:
Using the second mass for calculation, we get:
= m2/m1
= 100 g / 500 g = 0.20

 Conclusion: The kinetic coefficient of friction is 0.20.   The factors that could affect this experiment is that the string is not weightless and the pulley is not frictionless.The concept of Newton's first law was also experienced.  Objects more or remain in the same way, as long as no net force acts on it.
 Inclined Plane Formulas