Momentum and kinetic energy

In summary, the equations of momentum and kinetic energy of an object may contain the same symbols, but in an inelastic collision, the momentum is conserved while the kinetic energy may not be. This is due to the symmetry of Newton's Third Law and the fact that kinetic energy can be transformed into other forms of energy. Inelastic collisions are defined as collisions where kinetic energy is not conserved, while perfectly inelastic collisions result in the maximum loss of kinetic energy. The motion of the body is what ultimately determines the conversion of kinetic energy into other forms of energy.
  • #1
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why although the equations of momentum and kinetic energy of an object contains the same symbols m and v we note in an inelastic collision that momentum unlike the kinetic energy is conserved
 
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  • #2
Momentum will always be conserved because of the symmetry regarding Newton III. But kinetic energy does not need to be conserved because it can easily be transformed into heat, sound, deformation, etc. Note that the total energy still is conserved, just not kinetic energy. Moreover, inelastic collisions are defined by us to be a collision which does not conserve kinetic energy much like perfectly inelastic collisions are defined to be a collision where the final two objects "stick" together resulting in the maximum loss in kinetic energy.
 
  • #3
The kinetic energy is converted into other forms of energy. It all starts or ends with the motion of the body.

The momentum, whereas, is always there, before collision, after collision.
 
  • #4
that's now clear thank you
 
  • #5


Momentum and kinetic energy are two important concepts in physics that are closely related. Both of these quantities involve the mass and velocity of an object, and they are often used to describe the motion of an object.

The equations for momentum and kinetic energy contain the same symbols, such as mass (m) and velocity (v). However, it is important to note that these two quantities have different properties and behave differently in certain situations.

In an inelastic collision, which is a type of collision where the colliding objects stick together and move as one, we observe that momentum is conserved while kinetic energy is not. This means that the total momentum of the system before and after the collision remains the same, but the total kinetic energy changes.

This can be explained by the fact that momentum is a vector quantity, meaning it has both magnitude and direction. In an inelastic collision, the direction of the total momentum of the system remains the same, even though the objects may have changed their velocity and direction of motion. On the other hand, kinetic energy is a scalar quantity, meaning it only has magnitude. In an inelastic collision, some kinetic energy may be converted into other forms of energy, such as heat or sound, resulting in a decrease in the overall kinetic energy of the system.

Therefore, although the equations of momentum and kinetic energy contain the same symbols, they represent different physical quantities and behave differently in certain situations. Understanding the differences between these two quantities is crucial in accurately describing and analyzing the motion of objects.
 

1. What is momentum?

Momentum is a measure of an object's motion, calculated by multiplying its mass by its velocity. It is a vector quantity, meaning it has both magnitude and direction.

2. How is momentum different from kinetic energy?

Momentum is a measure of an object's motion, while kinetic energy is a measure of the energy an object has due to its motion. Momentum depends on both an object's mass and velocity, while kinetic energy only depends on an object's mass and speed.

3. How can momentum and kinetic energy be calculated?

Momentum can be calculated by multiplying an object's mass (in kilograms) by its velocity (in meters per second). Kinetic energy can be calculated by multiplying half of an object's mass by its speed squared (in meters per second).

4. What is the conservation of momentum?

The conservation of momentum is a fundamental law of physics that states that the total momentum of a closed system (where no external forces act) remains constant. This means that the initial momentum of objects before a collision is equal to the final momentum after the collision.

5. How does momentum and kinetic energy relate to each other in a closed system?

In a closed system, both momentum and kinetic energy are conserved. This means that while the total amount of momentum remains constant, the total amount of kinetic energy can change. For example, in a perfectly elastic collision, the total kinetic energy before and after the collision will be the same, while in an inelastic collision, some of the kinetic energy will be converted into other forms of energy.

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