This preview shows pages 1–3. Sign up to view the full content.
1
M1 Friction
PHY 151
I. Objective
Verify that the frictional force
f
is proportional to the normal reaction force
F
N.
Determine the coefficients of static and kinetic friction for two types of surfaces.
II Equipment
Adjustable incline plane, Teflon bottom pan, rubber bottom pan, dial spring scale,
weights, 100 cm ruler, plumb bob.
III. Introduction
When two objects are in contact they exert “contact forces” on each other.
For example
in fig.1 we show the two components of the contact force exerted by the floor on a block
of mass
m
on which a horizontal force
F
is acting.
One component labeled “
F
N
” in fig.1
is normal (perpendicular) to the contact interface between the floor and the block.
The
other component labeled “
f
” in fig.1 is parallel to the contact interface and is known as
“friction”.
Friction always opposes
motion (real or impending). The magnitude of
f
is
proportional to the magnitude of
F
N
.
If the block is moving with respect to the floor then the frictional force is called “kinetic”
(symbol
k
f
) and its magnitude is given by the equation:
kk
N
f
F
(1)
The constant
k
is known as the “coefficient of kinetic friction” and depends on the
nature of the two objects in contact.
This constant does not depend on the magnitude of
the normal force (
F
N
)
or applied forces.
If the block is not moving with respect to the floor then the frictional force is called
“static” (symbol
S
f
) and its magnitude is given by the inequality:
0
s
SN
f
F
(2)
F
N
mg
F
f
Fig.1
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document2
In other words
S
f
can take a range of values from a minimum value of 0 to a maximum
value of :
max
SS
N
f
F
(3)
IV. Experimental Method
A.
Coefficient of kinetic friction
This is the end of the preview. Sign up
to
access the rest of the document.
 Fall '10
 aa

Click to edit the document details