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17.6 Laws of Physics and Life -- Part 3
This is also the weight of the object.
There are illustrations of the third law in the text.
The total linear momentum of a system of objects remains the same unless acted on by an outside force.
Each point in an object is in motion as it rotates around a circle.
The equations for motion are similar to the equations for movement.
The relationships are shown in a table.
Along the path, there may be differences in angular velocity and acceleration.
As an object rotates around an axis, the magnitude of the linear velocity is constant, but the direction of the linear velocity is constantly changing.
The center of rotation is where the change in velocity points.
The body is accelerated toward the center of rotation.
Newton's second law states that a force pointing toward the center of rotation must act on the body because it is accelerated toward its center of rotation.
A centripetal force is needed for a body to move along a path.
The body moves in a straight line in the absence of a force.
An object twirled at the end of a rope.
The rope applies the centripetal force to the object.
An equal but opposite reaction force is applied to the rope by the object.
The force is moving away from the center of rotation.
2 is seen in Eq.
There is no need for energy to keep a body rotating.
The moment of inertia in motion is similar to mass in motion.
Mass elements in the body are located at different distances from the center of rotation when an object is in motion.
The sum of the moments of inertia of the mass elements in the body is the total moment of inertia.
The moment of inertia depends on the location of the center of rotation.
In general, the moment of inertia is calculated.
Table A.2 shows the moments of inertia for a few objects.
Torque is the tendency of a force to move an axis.
Torque is produced by a force.
The laws of movement are similar to those of movement.
The moment of inertia is similar to mass.
If an external Torque is not used, a body in rotation will continue its rotation with a constant angu lar velocity.
The second law is similar to Eq.
There is an equal and opposite reaction to every Torque.
If there is no unbalanced external force acting on the body, it can be shown that the angular momentum of the body is conserved.
Torques and forces can be applied to an object at the same time.
The net effect on a body is obtained by adding forces and Torques to a body.
When it's necessary to get the total force acting on a body, it's convenient to break it up into components.
The two-dimensional case is illustrated in Figure A.3.
A third axis is required for the analysis in a more general three-dimensional case.
A rotation can be either a clockwise or a counterclockwise direction.
The total Torque acting on a body is obtained by the addition of individual Torques each with the appropriate sign, if we designate one direction of rotation as positive and the other as negative.
A body is in static equilibrium if it's not moving fast.
A more rigorous definition is required in physics.
The distance through which the force acts and the product of force are what work is defined as.
The force is parallel to the direction of motion.
This is shown in Figure A.4.
The concept of energy is important.
References to energy are found in connection with many different phenomena.
The work was done by a force.
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