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Y15 ch10
1
Ch 10
Angular Momentum
•
(Recall) The torque of a force describes the tendency of
the force to cause or change rotational motion of the body
on which the force acts.
τ
=
Fl
=
Fr
sin
ϕ
=
F
tan
r,
τ
=
r
×
F
•
Angular acceleration of a rigid body is proportional to
the sum of the torques acting on it
;
the proportionality con
stant is given by the moment of inertia (for motions with
fixed direction of the axis of rotation).
α
=
1
I
τ
tot
,
(
τ
tot
=
I
α
)
,
τ
tot
=
τ
tot,external
The sum of the torques of all forces acting on a rigid body
is equal to the sum of the torques of external forces acting
on it.
Another form of this: If rotation about
z
axis then
τ
tot
z
=
I
α
z
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2
¨
Speed of a rolling sphere at the bottom of the incline;
two ways:
(a) Using conservation of energy
(b) Computing first acceleration, as in Example 10.7 – please
read.
f19
•
Rolling Friction
(p. 329) – please read.
Y15 ch10
3
10.4 Work, power, work theorem in rotational motion
(not on test 2)
W
=
Z
θ
2
θ
1
τ
d
θ
,
Power:
P
=
τω
Work theorem
W
=
K
2
−
K
1
=
1
2
I
ω
2
2
−
1
2
I
ω
2
1
– please read.
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4
10.5 Angular Momentum
•
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This note was uploaded on 03/19/2008 for the course PHYS 2305 taught by Professor Tschang during the Spring '08 term at Virginia Tech.
 Spring '08
 TSChang
 Physics, Acceleration, Angular Momentum, Force, Momentum

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