EMCH 200 – Statics
Homework 15
1. Determine the frictional force developed the surface contact. W is the weight of the crate.
cdot
frac
N
X
0
4
3
5
F
KineticFriction
N
K
F
Normal Force
N
0
3
5
2
Maximumstatic Friction
mu
N
s
right
left
N
0
3
5
1
right
left
N
0
8
2
1
Frictionforce
W
F
y
N
X
0
4
5
F1
UN
motion
occurs
2. Determine the minimum force P to prevent the 30 kg rod AB from sliding. The contact
surface at B is smooth, whereas the coefficient of static friction between the rod and the
wall at A is μs is 0.2.
mass
m
0
3
g
k
N
2
s
times
m
4
3
h
m
V
9
8
2
g
s1
1,5m2m
Forces at
C
A wall
NormalForce
FrictionForce
Forces B
N
A horizontal
mu
N
A
F
s
right
left
W
m
N
9
0
4
8
3
2
g1
NormalForce N
B vertical
right
left
N
A
0
P
x
f
2
F
y
W
N
A
0
P
F
Delta
mu
W
N
A
0
s
Sigma
right
left
W
M
N
A
0
B
4
3
2
F
varnothing
right
cdot
left
W
m
N
A
8
3
2
9
4
5
1
s
N
9
4
5
P
1
3. If a force of P = 30 N is applied to the handle as shown below, determine the largest
couple moment M that can resisted so that the wheel does not turn. The coefficient of
static friction between the belt and the wheel is μs = 0.3.
wheel radius
W
m
0
3
3
0
5
2
m
3
N
0
3
5
mu
3
s
from Approed force 7m Sigma
06mTorque
s
T
P
L
BeltFrictionEq
cdot
m
N
0
3
T
2
71
theta
frac
pi
N
T
2
es1
Rightarrow
p6
3
5
2
ei
m
N
0
4
8
5
T
2
p