Where is the force coming from to compress the spring

AI Thread Summary
The discussion centers on a physics problem involving a plank moving at a constant velocity connected to a mass via a spring. Participants express confusion about the source of force required to compress the spring, especially since the plank's uniform motion suggests no net force acting on the mass. The lack of clarity in the problem statement regarding friction and initial conditions is highlighted as a significant issue. Participants suggest visualizing the scenario without the spring to better understand the dynamics involved. The conversation emphasizes the need for clearer assumptions in the question for accurate analysis.
Lafith
Messages
4
Reaction score
0

Homework Statement



Given a plank is moved with uniform velocity v. To which a mass is connected by a spring of force constant k. What is work done by the external agent on the maximum compression of the spring

Homework Equations


Work done by spring=0.5*k*x2
Work-energy theorem: total work done =change in kinetic energy

The Attempt at a Solution


in order to compress a spring there has to be a force.but since it is given plank is moving with uniform velocity.where is the force coming from?
Since I couldn't figure or understand that I couldn't proceed further.
 

Attachments

  • Screenshot_2017-03-13-12-02-17-1.png
    Screenshot_2017-03-13-12-02-17-1.png
    20.8 KB · Views: 522
Physics news on Phys.org
The screenshot makes it a bit clearer. The "plank" is moved with constant velocity--but what about the mass, m? It seems we have to neglect friction.
 
  • Like
Likes Lafith
John Park said:
The screenshot makes it a bit clearer. The "plank" is moved with constant velocity--but what about the mass, m? It seems we have to neglect friction.
Then also why the mass moves...?
 
What would happen to the mass if there was no spring, and no friction, and the plank suddenly started moving at velocity v0?
 
  • Like
Likes Lafith
John Park said:
plank suddenly started moving
This is the necessary assumption, not made clear in the question.
 
  • Like
Likes Lafith
This is the necessary assumption, not made clear in the question.

It's not a terribly well written question--nothing about friction, for one thing--but I don't think anything else makes sense.
 
  • Like
Likes Lafith
John Park said:
It's not a terribly well written question--nothing about friction, for one thing--but I don't think anything else makes sense.
Ok then what is the work done by spring in this situation .is it negative or positive?
 
Is that the exact wording of the question?

There is no mention of it starting from rest?
 
Ok then what is the work done by spring in this situation .is it negative or positive?

Try to visualise what will happen if the whole system is at rest and then someone starts pulling the "plank". As I said, it might help if you start by imagining there's no spring and the mass is on a very slippery surface.

Also note that the question talks about "compression" of the spring.
 

Similar threads

Calculating the spring force constant K
Replies
14
Views
2K
Distribution of Energy when work is done on a system of 2 masses connected by a spring
Replies
17
Views
1K
Why can we move the spring with constant speed when we apply a force?
Replies
29
Views
2K
Why is my method for finding the spring constant incorrect?
Replies
17
Views
3K
A block dropping onto a spring system
2
Replies
58
Views
2K
Problem with when to use Force and Energy. What compresses spring/
Replies
3
Views
1K
Springs and Pulleys - Force analysis
Replies
18
Views
1K
Difficulty in deciding when to apply work energy theorem
Replies
2
Views
1K
Spring Problem Involving Variables and Constants Only
Replies
3
Views
1K
A block of mass m is dropped onto the top of a vertical spring....
Replies
8
Views
5K

Hot Threads

Recent Insights

Back
Top