Is Constant Velocity Essential for Understanding Work in Physics?

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Discussion Overview

The discussion revolves around the role of constant velocity in understanding the concept of work in physics. Participants explore whether this assumption is necessary and how it relates to various physics problems, including those involving forces like gravity and springs.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • Some participants note that many physics exercises assume constant velocity, which implies a net force of zero, and question the rationale behind this assumption.
  • Others argue that while constant velocity is a common simplifying assumption in introductory problems, it is not universally applicable, as there are scenarios where velocity is not constant.
  • A participant introduces the integral expression for work when velocity is not constant, suggesting a more complex relationship between force and motion.
  • One participant provides an example involving pushing a wagon up a hill, explaining that constant velocity is often used to simplify the problem and focus on gravitational potential energy without the complications of varying speeds.
  • It is mentioned that even in cases where a wagon accelerates, the work done can still be calculated based on the change in kinetic energy, indicating that the assumption of constant velocity is not strictly necessary for all scenarios.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of assuming constant velocity in physics problems. While some see it as a useful simplification, others highlight that it is not always applicable, leading to an unresolved discussion on the topic.

Contextual Notes

Some limitations include the dependence on specific problem contexts and the potential for confusion when transitioning between constant and variable velocity scenarios. The discussion does not resolve the implications of these assumptions on the understanding of work.

CollinsArg
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Hi! I've found some excercices and expanation of Work always consider a constant velocity, this is a net Force equal to cero. Like spring or gravity excercices related against a force applied. Does this relation with constant velocity has some usefull explanation why? Should I always assume this? (e
 
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CollinsArg said:
Should I always assume this?
No, you may find cases where the velocity is not constant. In these cases the work is defined using an integral expression:
$$W(t)=\int_{0}^{t}\mathbf{F}\cdot\mathbf{v}(t')dt'$$
I'm not sure if you are familiar with calculus though.
 
CollinsArg said:
Hi! I've found some excercices and expanation of Work always consider a constant velocity, this is a net Force equal to cero. Like spring or gravity excercices related against a force applied. Does this relation with constant velocity has some usefull explanation why? Should I always assume this? (e
It is usually a simplifying assumption written into first year physics problems.

Say, for instance that you are pushing a wagon up a hill. The problem asks how much work you have done pushing the wagon up the slope. But the author wants you to be thinking of gravitational potential energy (mgh). The author does not want you distracted worrying about pushing too hard and winding up with a rapidly moving wagon at the top. Or not pushing hard enough and having the wagon starting with high speed and coasting to a stop at the top with no work done.

So the author either may write that the wagon is pushed at a constant velocity or that the wagon is pushed slowly.

It is perfectly valid to consider the work done pushing a wagon with frictionless wheels on a level road. Naturally such a wagon will speed up as you go. The work done is still valid and will then correspond to the difference between the wagon's starting and ending kinetic energy.
 
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Likes   Reactions: NFuller, CollinsArg and Stephen Tashi
Thank you :)
 

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