Why can't we use cons of energy in this problem? (conceptual)

In summary, two pucks collide on a frictionless air-hockey table. Puck A, with a mass of 3.0 kg, initially travels at 3.5 m/s and collides with Puck B, which is at rest and has a mass of 5.0 kg. After the collision, Puck A moves away at a speed of 2.5 m/s and at an angle of 30.0 degrees from its initial direction. The final velocity of Puck B cannot be determined using the conservation of energy method since it is an elastic collision.
  • #1
jackspicer
2
0
Two pucks collide on a frictionless air-hockey table. Initally, puck A is traveling at 3.5 mls and puck B is at rest. After the collision, puck A moves away at a speed of 2.5 m/s and an angle of 30.0 from the initial direction. Find the final velocity of puck B. Puck A has a mass of 3.0 kg and puck B has a mass of 5.0 kg.

I know how to do the problem, but we can't we apply the conservation of energy methods because it is an elastic collision?
 
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  • #2
In inelastic collisions you can't use conservation of energy.
 
  • #3
He says that it is an elastic collision.
 

1. Why can't we use conservation of energy in this problem?

Conservation of energy is a fundamental principle in physics that states that energy cannot be created or destroyed, only transformed from one form to another. This means that the total amount of energy in a system must remain constant. However, there are certain situations where conservation of energy cannot be applied, such as in cases where energy is being added or removed from the system, or when non-conservative forces (such as friction) are present. In these cases, the total energy of the system is not constant, and therefore, conservation of energy cannot be used to solve the problem.

2. Can we always use conservation of energy in physics problems?

No, conservation of energy cannot be applied to all physics problems. As mentioned before, there are certain situations where the principle does not hold, such as when energy is being added or removed from the system, or when non-conservative forces are present. In these cases, other principles and equations must be used to solve the problem.

3. What are some examples of problems where conservation of energy cannot be used?

Some examples of problems where conservation of energy cannot be applied include problems involving rolling or sliding objects, problems with non-conservative forces such as friction or air resistance, and problems where energy is being added or removed from the system (such as in nuclear reactions or chemical reactions).

4. How do we know when to use conservation of energy in a problem?

Generally, conservation of energy can be used when the total energy of the system is constant, and when there are no non-conservative forces present. In other words, if energy is not being added or removed from the system, and if there are no forces that dissipate energy (such as friction), then conservation of energy can be applied to solve the problem.

5. Are there any limitations to the principle of conservation of energy?

While conservation of energy is a fundamental principle in physics, there are certain limitations to its application. As mentioned before, the principle cannot be used in cases where energy is being added or removed from the system, or when non-conservative forces are present. Additionally, the principle only applies to closed systems, meaning that no energy can enter or leave the system. In real-world situations, it can be difficult to find a completely closed system, so there may be some discrepancies in the application of the principle.

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