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MOMENTUM, IMPULSE, AND COLLISIONS - Coggle Diagram
MOMENTUM, IMPULSE, AND COLLISIONS
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Conservation of Momentum
During a collision, measurements show that the total momentum does not change:
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Conservation of momentum can also be derived from Newton’s laws. A collision takes a short enough time that we can ignore external forces. Since the internal forces are equal and opposite, the total momentum is constant.
For more than two objects
Or, since the internal forces cancel
Collisions and Impulse
During a collision, objects are deformed due to the large forces involved.
This quantity is defined as the impulse, J:
The impulse is equal to the change in momentum:
Since the time of the collision is often very short, we may be able to use the average force, which would produce the same impulse over the same time interval.
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Inelastic Collisions
With inelastic collisions, some of the initial kinetic energy is lost to thermal or potential energy. Kinetic energy may also be gained during explosions, as there is the addition of chemical or nuclear energy.
A completely inelastic collision is one in which the objects stick together afterward, so there is only one final velocity.
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Center of Mass (CM)
In (a), the diver’s motion is pure translation; in (b)
it is translation plus rotation.
There is one point that moves in the same path a Particle would take if subjected to the same force as the diver. This point is called the center of mass (CM).
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The general motion of an object can be considered as the sum of the translational motion of the CM, plus rotational, vibrational, or other forms of motion about the CM.
The general motion of an object can be considered as the sum of the translational motion of the CM, plus rotational, vibrational, or other forms of motion about the CM.
For two particles, the center of mass lies closer to the one with the most mass:
The center of gravity is the point at which the gravitational force can be considered to act. It is the same as the center of mass as long as the gravitational force does not vary among different parts of the object.
The center of gravity is the point at which the gravitational force can be considered to act. It is the same as the center of mass as long as the gravitational force does not vary among different parts of the object.
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