Is F=Kx Always Necessary for Spring Forces?

[navneet9431]

Is it necessary that the applied force F is equal to the spring force 'kx'?

 

[jbriggs444]

Is it necessary that the applied force F is equal to the spring force 'kx'?

Are you trying to invoke Newton's 2nd law or Newton's 3rd law? What, if anything, do either have to say about the situation?

 

[navneet9431]

I am not trying to invoke any law

Are you trying to invoke Newton's 2nd law or Newton's 3rd law? What, if anything, do either have to say about the situation?

 

[sophiecentaur]

Is the mass stationary?

 

[navneet9431]

No

Is the mass stationary?

 

[russ_watters]

View attachment 232217
Is it necessary that the applied force F is equal to the spring force 'kx'?

The way you've drawn the picture, it looks like F is a separate force applied to the mass, not the spring force. You'll have to tell us what the drawing means - you drew it! (presumably).

 

[sophiecentaur]

No

Make the spring as weak as you like. Would F be zero?

 

[navneet9431]

Yes,F(on right) is a separate force applied to mass m other than the spring force acting on the left side.

The way you've drawn the picture, it looks like F is a separate force applied to the mass, not the spring force. You'll have to tell us what the drawing means - you drew it! (presumably).

 

[Chestermiller]

Please write down for us your Newton's 2d law force balance equation on the mass M.

 

[navneet9431]

F-kx=ma

Please write down for us your Newton's 2d law force balance equation on the mass M.

 

[Chestermiller]

F-kx=ma

Perfect. Does that answer your question?

 

[russ_watters]

Yes,F(on right) is a separate force applied to mass m other than the spring force acting on the left side.

In that case it can have literally any value you choose to give it.

 

[navneet9431]

So it means that F=/=kx

Perfect. Does that answer your question?

 

[navneet9431]

But is it possible that F=kx in any condition?

 

[ZapperZ]

But is it possible that F=kx in any condition?

If the mass is stationary, or if F is applied in such a way that the mass is moving at a constant velocity. Look at the equation you wrote. What is "a" under these two situations?

Zz.

 

[navneet9431]

Thanks

If the mass is stationary, or if F is applied in such a way that the mass is moving at a constant velocity.

Zz.

 

[Kaguro]

But is it possible that F=kx in any condition?

YOU will choose that.

If you choose |F|>|kx|, then m won't be at rest, but will have a constant acceleration rightwards.
If |F| = |kx|, then you have achieved an equilibrium, nothing moves. (In lab, this is how we calculate spring constant, where F=mg)

If |F| < |kx|, then you will have the spring pulling m leftwards.