Is My Professor Wrong? Understanding the Work-Energy Principle

In summary, the conversation was about a disagreement with the professor's statement that work in must equal work out. The speaker argued that the work done by the mass and the work done by the spring are separate issues, while the professor pointed out that the speaker's calculation of work was incorrect due to the assumption of a constant force. The professor also mentioned a potential error in the calculation of k and the need to show all steps in solving problems.
  • #1
Frederick Wittman
1
0
See attached file. I believe my professor is incorrect. Work in must equal work out. We can imagine the work done by the mass as being a separate issue. Then, we recognize that the work done by the spring must be the same. Am I right? If not, why?


 

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  • #2
Your professor's comment is correct. Your calculation of the work done by the weight assumes a constant force, independent of compression x. However, the force law given (Hookes law) is variable and depends on the compression x. Because of the incorrect assumption, this led to you calculation of k being incorrect (too high) by a factor of two. After obtaining k, it is not clear that you performed the integral correctly in any case. You jumped from integral to answer. (Maybe your calculator allows this). Many problems require you to show all work and supply the missing step.
 

1. What is the Work-Energy Principle?

The Work-Energy Principle is a fundamental concept in physics that states that the work done on an object is equal to the change in its kinetic energy. This means that the amount of energy transferred to or from an object is equal to the amount of work done on it.

2. How is the Work-Energy Principle applied?

The Work-Energy Principle is applied in various situations where a force is applied to an object and causes it to move. It can be used to calculate the work done by a force, the change in an object's kinetic energy, and the final velocity of the object.

3. Can the Work-Energy Principle be violated?

No, the Work-Energy Principle is a fundamental law of physics and cannot be violated. This principle is based on the conservation of energy, which states that energy cannot be created or destroyed, only transferred from one form to another.

4. How does the Work-Energy Principle relate to other principles in physics?

The Work-Energy Principle is closely related to other principles in physics, such as the Law of Conservation of Energy, Newton's Laws of Motion, and the Principle of Virtual Work. It is also a key concept in the study of mechanics and is used to solve a variety of problems involving motion and forces.

5. Why is it important to understand the Work-Energy Principle?

Understanding the Work-Energy Principle is crucial for understanding the behavior of objects in motion and the role of forces in causing that motion. It is also essential for solving problems in physics and engineering, as well as for gaining a deeper understanding of the fundamental laws of nature.

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