PASCO ME-9502 Statics System - Manual (Page 49)

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M o d e l N o . M E - 9 5 0 2 S t a t i c F r i c t i o n o n a n I n c l i n e d P l a n e
0 1 2 - 1 2 8 7 6 B 45
Static Friction on an Inclined Plane
Imagine that the Friction Block is placed on the Inclined Plane, and one end of the plane is tilted upward until the
parallel component of the block’s weight begins to pull the block down the plane. Static friction holds the block in
place on the plane until the parallel component of the block’s weight is larger than the static friction. If the block
will almost — but not quite — start sliding, then the static friction is as large as possible and equals the parallel
component of the block’s weight.
One way to measure the coefficient of static friction,

k
, is to
find the maximum angle at which the plane can be tilted
before the block begins sliding down the plane. The compo-
nent of the weight of the block that is parallel to the plane, F

,
is Mg sin
, where M is the mass of the block. The normal
force, F
N
, is the perpendicular component of the block’s
weight, or F

= Mg cos
. The force of static friction, f
s
, is the
coefficient of static friction,

s
, multiplied by the normal
force. Therefore, f
s
=

s
Mg cos
.
When the block is at rest, the static friction force equals the
component of the block’s weight that is parallel to the incline,
or
. Solving for the coefficient of
static friction,

s
, gives the following:
Procedure
1. Mount the Inclined Plane on the Statics
Board and set the angle to zero. Place the
Friction Block on the Inclined Plane.
2. Carefully raise one end of the Inclined Plane
until the Friction Block just begins to slide.
Record the angle,
.
3. Switch the Friction Block to a different sur-
face material and repeat the procedure.
Data Table
Calculations
• Calculate the coefficient of static friction for both wood and felt.
Question
• How does the coefficient of static friction for wood compare to the coefficient of static friction for felt?
Surface Material Angle Coefficient of Static Friction
Wood
Felt
F

F

Object

F 
Inclined
plane
f
s
Figure 8.5: Static Friction Diagram
Mg

sin

s
Mg

cos =

s
Mg

sin
Mg

cos
--------------------

tan = =
Figure 8.6: Increase the Angle