5
$\begingroup$

Let's say a body highly deformable like a clay is placed in space very far away from any celestial body. And a very high magnitude of force is applied on it in one direction as shown below.

Image missing :(

Will there be any deformation in the body due to the inertia of the point 'B' or there is no other opposite force so there will be no deformation, Which case is going to happen?

Improve this question
$\endgroup$
3
  • $\begingroup$ If someone knows this, a similar question but in rotational motion is here, link $\endgroup$
    – Aarunya Kumar
    Commented yesterday
  • 7
    $\begingroup$ Hang a melon up so that it is free to move in the horizontal direction. Find a martial artist and ask them to punch the melon very hard. What do you think would happen? $\endgroup$
    – Vokaylop
    Commented yesterday
  • $\begingroup$ You don't even need to state that the object is "highly deformable". Under the right acceleration and speed, any body can be deformed. Perfectly rigid objects do not exist. - - - Gravastars: Hold my bee... perfect fluid. $\endgroup$
    – Mindwin Remember Monica
    Commented 14 hours ago

4 Answers 4

Reset to default
6
$\begingroup$

The object will deform. Point A will initially accelerate at a higher rate than Point B.

The simplest model of a deformable object is one made up of a bunch of point masses connected by springs (often stiff springs). There are more complicated ways to think about it, but this is probably the easiest. With this model it's pretty easy to see that if you apply a force to Point A, the springs will initially apply no forces between points A and B, and point A will accelerate. As it moves, the spring gets compressed, and this begins applying a force to point B. At first, this force will be smaller than the applied force. Over time, you will compress the springs more and more until they reach the new equilibrium. When this happens, point A and B will be accelerating at the same rate, just like in the rigid body case. But in the transient period before that, they accelerate at a different rate.

Improve this answer
$\endgroup$
4
  • $\begingroup$ So this means, the opposite forces which causes it to deform is actually the internal forces in between the atoms. If we increase force with time for infinite period, then their nucleus should collide and form a radioactive substance also, to add catalyst there should also be heat and radiation from outside to the body, as @BioPhysicist told about energy dissipation, to avoid that also their should be external energy to it in order to make a radioactive substance. Am I right or their is much depth in this concept which I need to study first in order to ask this? $\endgroup$
    – Aarunya Kumar
    Commented yesterday
  • $\begingroup$ Also, is there same case in link, where the rocket will bend very little as the spring will bend (almost negligible). And there will be completely translational motion $\endgroup$
    – Aarunya Kumar
    Commented yesterday
  • 1
    $\begingroup$ I would say it points in that general direction, but I would be warry of trying to take it to such extremes with such a simple model. "All models are wrong; some are useful." This model is useful for most interactions, but if you're getting to the point of causing fusion then there's going to be a lot of important higher order effects to model. And the dissipation into heat requires understanding how motion is woven into the definition of temperature. But it does point in that general direction. $\endgroup$
    – Cort Ammon
    Commented 17 hours ago
  • $\begingroup$ springs would imply elastic deforming - the question says the body is "like clay", so while the "point masses and springs" help understand how one can model a body with distributed mass, it won't give the right end result here. With a clay-like body, we'll definitely see some plastic deformation, I'd think. Not sure how to model that in an easy way, though. $\endgroup$
    – Syndic
    Commented 43 mins ago
5
$\begingroup$

No body is completely rigid. Sound (mechanical waves) will always travel through the object. So yes, there must be deformation, at least comparing the case of no force to suddenly applying the force.

However, with dissipation you could reach a point where all parts of the object are accelerating together, so you could say there is no deformation at this steady state, at least compared to other instances in time at the same steady state.

Improve this answer
$\endgroup$
1
  • $\begingroup$ So the opposite force which causes it to deform is produced by mechanical waves inside the body, that means in link, mechanical wave will more in the upper part of the rocket which will produce internal force more on the upper part of the rocket and will cause it to bend, having both rotational and translational motion. Am I Right? $\endgroup$
    – Aarunya Kumar
    Commented 23 hours ago
4
$\begingroup$

Yes, it will. I see no principal difference from this situation and similar situation when deformable body (all do, only "deformability" degree is different) moving with speed $v_0$ has to experience high deceleration, like in a car crash tests. If you will apply same in magnitude force (but accelerating this time) to a car like the forces experienced in a car crash tests,- you will get same car crash effect upon "speeding-up".

Improve this answer
$\endgroup$
3
  • $\begingroup$ Is there's the same case in link, the rocket will have both rotational and translational motion. If the rocket is moving horizontal with speed v and the lower part of the rocket will collide with let's say a wall, then there will be both rotational and translational motion and it's going to be the same case with inertia of rest like in this question? If yes, then what's wrong if we look this case as 2nd comment below the '@CortAmmon' answer? $\endgroup$
    – Aarunya Kumar
    Commented yesterday
  • $\begingroup$ I see this as an entirely different question, so you should post it separately. $\endgroup$
    – Agnius Vasiliauskas
    Commented 23 hours ago
  • $\begingroup$ I have, but didn't get the answer :( both answer makes sense to me to be correct in that rocket question $\endgroup$
    – Aarunya Kumar
    Commented 23 hours ago
1
$\begingroup$

@Cort Ammon's answer is very good but as they say "all models are wrong and some are useful". In this case the masses and spring model doesn't quite work for a substance such as clay because if a very high force is applied the "springs will break" and the "masses" slide relative to each other. Actually most substances have an elastic phase where small forces are applied and a plastic phase where a higher force is applied. The springs and masses model only works in the elastic phase. Initially the body will deform but then when the force is removed it will spring back to its original shape. If a higher force is applied though, sufficient to push the body into its plastic phase the body's molecules will slip past each other and it will be permanently deformed.

Improve this answer
New contributor
Mark Paice is a new contributor to this site. Take care in asking for clarification, commenting, and answering. Check out our Code of Conduct.
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.