This preview shows page 1. Sign up to view the full content.
Homework 7 Hints
Please first read the Sample Problems 3/2 and 3/3 on page P128129.
3/2.
x
axis should be selected along the slope. It is easy to calculate N in terms of mg and
. Now, you have to judge whether you should use
15
θ
=
D
s
μ
or
k
(the coefficient of kinetic
friction).
(a). Notice, movement is down and friction is up.
Check the impending motion:
Calculate the (friction) static force
static
F
to keep the mass static on slope from
. In the
impending motion, mass will immediately start to move, but does not move yet. Therefore
0
x
F
=
∑
x
a
is
equal to zero. Compare
with
127
static
FN
=
s
N
to see if movement occurs or not. In this case,
movement does occur.
x
x
Fm
a
=
∑
is used to calculate
.
a
k
is used to compute kinetic
friction.
m/sec
1.12
a
=
2
down.
(b). (c). Repeat above procedures. Notice: friction is up. (c).
2.04
a
=
m/sec
2
3/21.
This is the end of the preview. Sign up
to
access the rest of the document.
This note was uploaded on 09/27/2008 for the course ME 212 taught by Professor Staff during the Spring '05 term at Cal Poly.
 Spring '05
 staff

Click to edit the document details