Calculating Net Work Done by 500g Mass on Unstretched Spring

In summary, the conversation discusses the calculation of net work done on a mass attached to an unstretched spring when released and reaching its lowest point. The work done is determined using the work-kinetic energy theorem and the work-potential energy theorem, with a focus on the change in potential energy for each force acting on the mass. The concept of work is further clarified and the importance of thinking through problems instead of relying on others is emphasized.
  • #1
habibclan
55
0

Homework Statement


A mass of 500 g is attached to the bottom of an unstretched spring attached to the ceiling, and has a spring constant 10 N/m. The mass is then released. What is the net work done on the mass between the point where it was released and the lowest point that it reaches?


Homework Equations



Wnet= F.d

The Attempt at a Solution



The point at which it is released, v=0 and the lowest point is a turning point therefore v=0. So Wnet=delta K= 0 as velocity is 0 both times. Would the work done be 0 J then? Thanks in advance for any help!
 
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  • #2
This is also why there is a "work-potential energy theorem":

W = - delta_PE .

This is the work done by each force. Consider that there are two acting on the mass, gravity and the spring's restoring force, so you'll need to look at the change in potential energy for each as the mass goes from one rest point to the other.

(There is a more precise way to describe this situation using mechanical energy conservation, which may clarify things further.)
 
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  • #3
0 J? Are you serious? I think you are maybe asking too many questions and not thinking enough. This has afflicted people on this forum before. Don't let yourself be one of them. Why don't you equate gravitational potential energy change with spring potential energy change if v=0 at both points?
 
  • #4
Sorry :$. It's just that I'm not really good with the concept of work. I read the textbook and did all the recommended questions but this was from a practice midterm. I'll try not to post as much now and try to think them through. But I only post questions if I try them at least 3-4 times and still don't get them! My exam being on Tuesday doesn't help much as I've got to cover everything in a few days =(.
 
  • #5
Ok, but it still seems to me you could get more of these questions if you would just think harder. I believe you are pretty good. Some people do use PF as a substitute for thinking. Don't be one of them. 0 J? Really? Can you explain your thinking on that? Work=force*distance and work is relative to the force doing the work. If you think of gravity as doing the work then the result is negative the result of if you think of the spring doing the work. So maybe the correct answer is 0 J. So if net work=gravity plus spring then you are correct. Sorry for being so crabby.
 
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  • #6
I was thinking of the work-kinetic energy theorem were Wnet= delta K. But maybe I should always stick to the equation: Ki + Ugi + Wext= Kf + Ugf + Delta E (thermal), and plug in things to see where the conversion is occurring. My textbook gives too many formulas which creates a lot of confusion!
 
  • #7
No, you already have it. In the sense you are talking about the net work is 0 J. You really basically understand most of the stuff you post. It's my problem that I don't understand that you already understand.
 

FAQ: Calculating Net Work Done by 500g Mass on Unstretched Spring

How do you calculate the net work done by a 500g mass on an unstretched spring?

To calculate the net work done by a 500g mass on an unstretched spring, you can use the formula W = ½kx², where W is the work done, k is the spring constant, and x is the displacement of the spring. The spring constant can be found by dividing the force applied to the spring by the displacement. Once you have the spring constant, you can plug in the values for x and solve for W.

What is the unit of measurement for net work?

The unit of measurement for net work is joules (J). This is because work is equal to force multiplied by displacement, and both force and displacement are measured in units of newtons (N) and meters (m) respectively. Therefore, the unit of measurement for work is N*m, which is equivalent to joules.

Can the net work done by a 500g mass on an unstretched spring be negative?

Yes, the net work done by a 500g mass on an unstretched spring can be negative. This can happen if the force applied to the spring is in the opposite direction of the displacement. In this case, the work done by the force would be considered negative, indicating that energy was taken away from the system.

How does the mass of the object affect the net work done on the spring?

The mass of the object does not directly affect the net work done on the spring. However, it does affect the force applied to the spring, which in turn affects the spring constant and displacement. A heavier object would require a greater force to displace the spring, resulting in a higher spring constant and potentially a larger displacement. These factors would ultimately affect the net work done on the spring.

Are there any other factors that can affect the net work done by a 500g mass on an unstretched spring?

Yes, there are other factors that can affect the net work done by a 500g mass on an unstretched spring. These include the angle at which the force is applied, the presence of friction or other external forces, and the elasticity of the spring. These factors can impact the displacement and force applied to the spring, ultimately affecting the net work done.

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