MOTION OF ROTATION
Hoga Saragih
• The item in question is a tough thing to
particular form that does not change, so that its constituent particles are in a fixed position relative
each other.
• Of course, any real object can vibrate or
change shape when worn style. But this effect
often small, so the concept of an ideal rigid body
very useful as a good approximation.
• The term is a pure rotational motion of all points on the object
moving in a circle and the center of all this circle
located on a line called the axis of rotation.
A. Magnitude ANGLE
• To describe the rotational motion, we
use the angle magnitudes, such as
angular velocity and angular acceleration.
• The size of this scale is defined by
analogy to the magnitudes of
corresponding to the linear motion.
• Each particle moves in a circle,
and each take a corner
the same.
• Each point on the rotating object
moving around a fixed axis
a circle whose center
located on the axis and radius r, the distance
The point of the axis of rotation.
• The angle is usually expressed in degrees,
but mathematics circular motion away
easier to use radians as
the size of the angle.
• One radian (rad) is defined as
angle of the edges connected
by an arc whose length is equal to
radius.
• average angular speed is defined by
analogy to the usual linear velocity. If
usually we use a linear displacement,
Now we use the angular displacement.
• Speed of instantaneous angle as the angle
very small objects through the hose
a very short time.
• Speed is usually expressed in a corner
radians per second
• Note that all points on the rigid body
rotates with the same angular velocity,
for each position on a moving object
through the same point in time lapse
the same.
• Accelerating the corner, by analogy to
ordinary linear acceleration, defined as
changes in angular velocity divided by time
required for this change.
• Each particle or a point on the rigid body
rotation has, at any time, the speed
v linear and linear acceleration a.
• We can connect the magnitude scale
This linear, v and a, for each particle, with
angle magnitudes, and, for
object rotates as a unit
• So, although the angular velocity for each
point on the object that rotates at any time,
linear velocity v is greater for points
more distant from the axis.
ω α
• In Example 8-5 the image of a wheel
uniformly rotating against the direction of the needle
hours, two points on the wheel, with a distance r1
and r2 from the center, has a linear velocity
different because of the distance
at different time intervals
the same. Because r2> r1, the V2> V1. but
The second point has an angular velocity
same as taking the same angle
the same time interval.
• Acceleration of radial or "sentripental" and
direction toward the center of a circular path
particles.
• So the greater the acceleration sentripental if
you further and further away from the axis of rotation.
• We can connect the angular velocity
with frequency, where f is the number of
rounds per second a lap in touch
the angle 2pi radians. Means that in general,
speed-related frequency f
angle.
• The unit of frequency, cycles per second
given a special name that is hertz
• The time needed for one
complete rotation is called the period
Kinematics equations for motion
uniformly accelerated rotation
• We reduce the equations
the importance of linking
acceleration, speed, and distance to
uniform linear acceleration situations.
Motion Mengelinding
• Movement of rolling a ball or
banya wheels found in living
daily: a ball mengelinding
across the floor, or wheels and tires
or spinning bikes along the way.
• rolling without slippage can be directly
analyzed and depending on the friction
static between the rolling bodies
and floors.
• Friction is static because the point of contact
objects that roll to the floor
at rest on any
time. (Kinetic friction applies if,
for example, you brake too
hard that the tires slip, or you
accelerating so fast in such a
you "burn rubber", but this
is a difficult situation)
• Scrolling without slippage involves rotation and
translation. But there are simple relations
between the rate of linear axle and speed v
angle of the wheel or ball mengelinding.
• Figure 8a shows an 8-ball
roll to right without any slippage. At the time of
described, the point p on the wheel
contact with the ground and are in
rest for a moment. Axis speed
wheel in the center of C is v.
• In Figure 8-8B we put ourselves
wheels on the frame of reference-that is, we
moving to right with velocity v
relative to the ground. In the framework
this reference, located in the C axis
at rest, while the ground and the point
P moving left with velocity-v
as illustrated. Here we
see the pure rotation
Torque
• So far we have discussed
rotational kinematics, rotational motion description
the angle, angular velocity, and
angular acceleration.
• Now we discuss the dynamics, or
cause, the motion of rotation. Together we
find an analogy between the linear motion
and rotation for the description of motion, equivalent
rotational dynamics also exist.
• To create an object object
began to rotate around the axis of the apparent
required style.
• But the direction of this force, and where
granted, it is also important. Take, for
For example, everyday situations, such as door
in Figure 8-10. (Viewed from above).
• If you experience a force perpendicular to F1
door as described, you will be seen
that the magnitude of the F1 game, the faster the doors open.
• But now if you apply a force with
The first major point that is closer
with hinges, say f2, in the figure 8-10,
you will see that the doors will open
so quickly. Smaller style effects. And
indeed, be seen that the angular acceleration of the door
proportional not only with great style,
but also the perpendicular distance from the axis of rotation
to the line style of work.
• This distance is called the arm of force, or torque arm,
of style, and r1 and r2 are labeled for both
in Figure 8-10 style.
• Thus if r1 r2 triples, then
angular acceleration of the door will be three times more
large, with great regard to the same style.
In other words, if r1 = 3R2, then F2 must
F1 three times to produce acceleration
the same angle.
• Thus, the angular acceleration
directly proportional to the product of force
with arm style. The results of this so-called
style torque around the axis, or more generally
is called torque. Means the angular acceleration
alpha of an object is directly proportional
the total torque is given.
Posted By Febri Irawanto
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