PASCO ME-8574 DISCOVER FRICTION ACCESSORY - Manual (Page 2)

Discover Friction Accessory 012-07552A
2
Sliding Friction Equations
The purpose of this experiment is for students to
construct the relationship between frictional forces
and the normal force on an object. These general
equations can then be used to predict both the
static and kinetic frictional forces present in many
situations.
F
S
=
µ
S
F
N
F
k
=
µ
k
F
N
The resulting graph will reveal that the frictional
force increases to a maximum, and then levels off
at a constant value as the tray moves. Both the
maximum static frictional force and kinetic
frictional force can be obtained from the graph.
Repeat this procedure three more times increasing
the mass of the friction tray by 500 grams each
time. Finally, a graph of static frictional force vs.
normal force can be created. The slope of this
graph is the coefficient of static friction. In a
similar manner, a graph of the kinetic frictional
force vs. normal force can be created and
analyzed. For more repeatable results, the
Motorized Cart (ME-9780 – ME-9781) can be
used to pull the friction trays from rest.
A small piece of string should be tied between one
of the friction trays and the force sensor. With no
force on the sensor, the zero (tare) button should
be pressed. This should only be performed once!
Next, place the friction tray on a fairly rough
surface such as carpet or a sidewalk and load it
with one 500 gram mass bar. Click on the Start
button to begin collecting data, then pull on the
force sensor until the friction tray breaks free.
Continue to pull, such that the friction tray moves
with constant speed.
Coefficients of Friction for Various Surface
Combinations
Students can repeat the above experiment with
different surface combinations to determine the
relationship between coefficient of friction and
surface roughness. The surfaces on the bottom of
the Discover Friction Accessory were chosen to
provide a wide variety of friction coefficients.
Figure 1: Discover Friction Accessory used with the PASport Force Sensor