Work done by force acting on a spring

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Discussion Overview

The discussion revolves around the work done by a force acting on a spring within a horizontal mass-spring system oscillating on a frictionless surface. Participants explore the implications of forces acting on the spring, particularly the force exerted by a wall, and the conditions under which work is done or not done on the spring.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants assert that the wall exerts a force on the spring, questioning the nature of this force when the wall is stationary.
  • There is a discussion about whether the work done by the wall on the spring is zero due to the wall's displacement being zero.
  • Some participants propose that while the wall does no work on the spring, the force exerted by the mass on the spring does perform work since the mass is in motion.
  • Others argue that the net work done on the spring must be zero if the net force acting on it is zero, leading to a contradiction regarding the work done by the wall and the mass.
  • Participants debate the definitions of work and net force, with some emphasizing the importance of distinguishing between individual forces and net forces.
  • There are conflicting views on whether work can be negative and how it relates to the energy transferred in the system.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the relationship between the work done by the wall and the work done on the spring. Multiple competing views remain regarding the definitions and implications of work in this context.

Contextual Notes

There are unresolved assumptions regarding the definitions of work and the conditions under which it is calculated, particularly in relation to the displacement of the points of application of forces acting on the spring.

  • #31
Studiot said:
Do you think that the change in position of the mass results in a change in its potential energy, because the spring is then extended?
I thought you disconnected the spring.
 
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  • #32
Sorry if the lines of thought were disconnected.

This is back to the original setup.

Force F is applied to draw back the mass attached to the spring to s1 and

1) Held in position.

2) Then it is released (F is removed)

Do you think the mass has gained potential energy as a result in (1) and (if so) does it still possesses this energy at the moment of release of F or just after (2) ?
 
  • #33
Studiot said:
Do you think the mass has gained potential energy as a result in (1) and (if so) does it still possesses this energy at the moment of release of F or just after (2) ?
The system has gained spring potential energy. And that potential energy depends only on the amount the spring is stretched from its equilibrium position.

So: Yes, the system has PE when it is held in position (1) and immediately after the force F is removed (2).
 
  • #34
As soon as the spring is stretched it exerts a pull on the mass, which will move the mass if we let go.

What is the difference between that pull and the pull on the mass due to gravity, which would draw it down if we removed the table?
 
  • #35
Studiot said:
As soon as the spring is stretched it exerts a pull on the mass, which will move the mass if we let go.
Sure.
What is the difference between that pull and the pull on the mass due to gravity, which would draw it down if we removed the table?
What point are you trying to make? (You're losing me.)
 
  • #36
The objective is an energy balance or accounting.

(It's not a trick 'onest guv)

I'm merely observing that we can (I think) say that the mass has potential energy due to the elastic energy stored in the spring and thereofe the pull exerted by the spring.

This is eventually transferred to the mass as kinetic energy when it oscillates and forms the energy of the oscillation ie that which is transferred back and fore between KE and PE.

I want to end up by observing that the force F does work on the mass, which in turn does work on the spring when pulled out so the net energy of the mass does not increase when it has reached a stop at the maximum s1
 
  • #37
Studiot said:
The objective is an energy balance or accounting.

(It's not a trick 'onest guv)

I'm merely observing that we can (I think) say that the mass has potential energy due to the elastic energy stored in the spring and thereofe the pull exerted by the spring.

This is eventually transferred to the mass as kinetic energy when it oscillates and forms the energy of the oscillation ie that which is transferred back and fore between KE and PE.

I want to end up by observing that the force F does work on the mass, which in turn does work on the spring when pulled out so the net energy of the mass does not increase when it has reached a stop at the maximum s1
I prefer to say that the system (really the spring) has potential energy, not just the mass. (For the same reason I think it is misleading to talk about the gravitational PE of a mass--it's really the PE of the mass-earth system.)

The force F does work on the system. The mass essentially transmits the force to the spring, which gets spring PE as it is stretched. When the mass is allowed to oscillate, the spring and mass exchange energy.

I don't see the issue. (Or how it relates to the OP's concern.)
 
  • #38
it's really the PE of the mass-earth system.)

Yes that's true enough.
Thanks for your patience.
 

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