Jacob Vaught and Hassan Aslam
Texas A&M University
College Station, TX 77843, US.
Abstract This lab report will be covering the general concept of static friction and kinetic friction. With the usage
of camera and interface with computer we will find out these forces. One will use a small piece of wood (in
rectangle shape) with two different surfaces on both sides and that wooden pieces will be dropped from certain
angle to get the values of static friction and static kinetic. Along with these forces, this lab will also cover the
uncertainties that are with the calculated values.
Keywords: Angle, static friction, static kinetic
Introduction
The goal of this lab is to get familiar with the concept of coefficient of static friction and kinetic friction. Static
friction is a force of friction between two or more objects (solids) that are not in action or are on rest relative to one
another. While on the other hand, kinetic friction is a force that takes place between the moving surface. The body
in action on the surface experiences a force in the opposite direction of its movement.
The second major concept that will be used is the concept of vectors. The data we will get from the interface will
be in the face of vectors. Vectors play an important role in the velocity and acceleration of the object. This will be
going to give us a close look at the importance of vectors while dealing with the concept of static friction and
kinetic friction.
The third important concept that this lab will be covering is the concept of uncertainty. Uncertainty is a small error
that one finds in any calculation. As we are humans and it is proven that whatever calculation we do, the results are
not exactly there is always a slight error in that result. The slight error in the calculation is the uncertainty and this
lab will be covering the uncertainties with the values of static friction and kinetic friction.
The major equations that we are going to use through this experiment include the equation to find the angle, static
friction, kinetic friction, and the uncertainty along with the results.
Angle at which pieces starts to slide down = sin^-1 (opposite / hypotenuse)
Static friction = tan θ
Kinetic friction = tan θ – (ax/gcos θ )
Uncertainty for static friction = d/d θ (tan θ ) .50
Experimental Procedure
The first thing one needs to find is the angle at which the object starts to slide down. In order to find the angle, we
need the dimensions of tringle (height: 36cm and hypotenuse: 74cm). We will use a simple trig identity to find the
angle. We use the identity of sin inverse which will give us an angle of 29.11 degrees for the plan surface. We need
to find static friction for two surfaces one for the plan surface and one with the rubber surfaces. So, we will take
two trials one for the plan surface and one for the rubber surface. We will use the same method but different to find
the angle at which the object will slide down on the rubber surface. (Angle for rubber surface: 40.44 degrees). Then
we will use that angle to find the static friction and the uncertainty along with it through the equation given above.
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