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Chapters 9 and 10: Rotational Motion
We’ve considered the physics of the motion of
particles
, and the motion of the center of
mass of extended objects.
But extended objects can also
rotate
about an
axis.
Rotation and angles
Think about a
rigid body
that rotates about a
fixed axis
. First, we need to sort out a better
‘unit’ for angles
We’ve been using
degrees
[0:360], but there is
a better ‘unit’ we can use called
radians
1 radian is defined as the angle subtended at
the center of a circle by an arc with length
equal to the radius of the circle
all round the circle,
1 rad = 57.3
o
Angular velocity
Define an
angular velocity
as the
rate of change of an angle
units are radians/second
who has the larger angular velocity, the
boy or the girl?
boy
girl
Angular acceleration
Define an
angular acceleration
as the
rate of change of the angular velocity
units are
radians/second
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