T
T
-Mg
Homework hints:
Free body diagram
F
a
fixes the acceleration of
m
A
+m
B
.
Notice that this is also the acceleration
of
m
A
and
m
B
individually
.
Now consider what force would be needed
to give e.g.
m
B
that acceleration and what
provides that force.
Man pulls down with
F = -T
, but that
F
is
NOT a force acting
on him and the cage.

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FBD
θ
F
G
mg
−
f
G
Fsin
θ
Fcos
θ
The block is pulled at constant speed
v
with
m
,
F
and
θ
given. What is
μ
k
?
X
x
F
Fcos
f
ma
0
=
θ −
=
=
∑
f
Fcos
=
θ
But
k
f
N
Fcos
= μ
=
θ
y
y
F
Fsin
N
mg
ma
0
=
θ +
−
=
=
∑
Along x
k
F
cos
N
μ
=
θ
Need
N
Along y
N
mg
Fsin
=
−
θ
So,
k
F
cos
mg
Fsin
μ
=
θ
−
θ
Last class:
N