How Does the Action-Reaction Principle Apply to a Screw Fastener and Nut?

[Mark2020]

Let's agree on this: the nut acquires a constant acceleration in the linear actuator by increasing the input power (and force) constantly. While the nut travels from one end to the other, what will be the momentum of the rest of the system?

Will it follow or will it go against the nut? Please take into consideration there are no rectilinear forces along the length of the leadscrew (or the linear actuator).

 

[jbriggs444]

Let's agree on this: the nut acquires a constant acceleration in the linear actuator by increasing the input power (and force) constantly. While the nut travels from one end to the other, what will be the momentum of the rest of the system?

Will it follow or will it go against the nut? Please take into consideration there are no rectilinear forces along the length of the leadscrew (or the linear actuator).

You continue to post contradictions.

If there is no net linear force on the nut then the nut cannot have a constant non-zero linear acceleration. There is a net linear force from actuator on nut in this case. Otherwise it would remain motionless where it started at rest. I claim that this net linear force arises primarily from the normal force of lead screw threads on nut threads.

Let us assume that you are indeed ramping up power to the actuator, increasing the spin rate of the lead screw at a constant rate. Let us agree that this results in a constant non-zero acceleration of the nut down the axis of the actuator.

Then it follows that as the nut accelerates one way down the length of the actuator, the lead screw and the rest of the actuator mechanism will be accelerating in the opposite direction. This is called "recoil".

 

[Mark2020]

Then it follows that as the nut accelerates one way down the length of the actuator, the lead screw and the rest of the actuator mechanism will be accelerating in the opposite direction. This is called "recoil".

Again, that would be true if we had to do with collinear forces. In order this to take place you have to replace the leadscrew with an unthreaded rod. Then the "recoil" force will work that will be interpreted to system's opposite momentum.

In our case, the leadscrew turns just to one direction. The advancing of nut and the system as a whole is limited/depended on the direction of rotation of the leadscrew. So, a clockwise rotation of the leadscrew will force the nut to advance counterclockwise that appears moving to the right. This means the system cannot develop the known collinear "recoil" force but just over the leadscrew. Conclusively, since the leadscrew turns only to one direction (never both) at a time, then the "recoil" force that applies to the rest of the system will have the same direction as the force (non collinear force) makes the nut evolving to the right. In other words, the nut and the system will have the same magnitude and same direction of momentum.

 

[jbriggs444]

Again, that would be true if we had to do with collinear forces. In order this to take place you have to replace the leadscrew with an unthreaded rod. Then the "recoil" force will work that will be interpreted to system's opposite momentum.

Again, there is no magic that occurs when you change the name you choose to label a force with.

 

[Mark2020]

I just would like to thank you for your participation in this discussion. I was looking to test some of my ideas with the experts of this forum.

Thanks everybody!

 

[berkeman]

Thread closed temporarily for Moderation...

 

[Dale]

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