Free Body Diagram
Recipe
1/Define preferred directions:
1
st
the direction of motion and the direction perpendicular to it
2/Project the
force
s
, on those two directions
3/ Apply Newton’s 2
nd
law on each direction separately
a)
There is no motion in the di
rection perpendicular to the direction of motion
Therefore,
the acceleration in that direction
is zero and so the projection
of the net force in that direction is zero too
b)
The pro
jection of the net force in the
direction
of motion
is
a
m
.
4/ Using
the information in
3/
in a) we can in extract one of the forces if the second is known and make use of it in
expression
b)
F
ollowing the comments of stud
ents I have added below
the
demonstration
that the angle between the weight
w=
m
g
and the direction
of
N
equal
the slope
See example below
:
A skier
of mass m
is sliding down a ski slope at a constant velocity. The slope makes an a
ngle of
above the horizontal
direction.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '09
 HUANG
 Force, Friction, Mass

Click to edit the document details