What happens when.........

Nothing happens because the situation could not occur.

If a force is unstoppable, no object is immovable.

If an object is immovable, no force is unstoppable.

The riddle is just a set of words with no meaning.

You might as well say "What happens when you put an unmeltable object in a flame that melts everything?". If either one exists, the other cannot.

But an unstoppable force could still collide with another unstoppable force. What would happen then :O ?

Nice answer btw

Nothing, the question is a paradox, in that by definition, if an unstoppable force exists there is no immovable object and vice versa.

An interesting point is; what is immovable, it surely won't be anchored to something else move immovable than it, so it itself has to be infinite mass.

Right, so we have an infinite force meeting an infinite mass. Lets clean the numbers: We have a force of 1 meeting a mass of 1.

"unstoppable force could still collide with another unstoppable force"

True! Therefore if an unstoppable force was hit with an unstoppable force, they would simple swap roles.

Newton's laws of motion: For every action there is an equal and opposite reaction.

When you get infinities in your calculations, that's a pretty good sign you have gone wrong somewhere.

An unstoppable object would be one with infinite momentum, ie m x v squared = infinity. Infinite m or v are impossible.

It should be pointed out that this practice of refusing infinite values for measurable quantities does not come from a priori or ideological motivations, but rather from more methodological and pragmatic motivations. One of the needs of any physical and scientific theory is to give usable formulas that correspond to or at least approximate reality.

As an example if any object of infinite gravitational mass were to exist, any usage of the formula to calculate the gravitational force would lead to an infinite result, which would be of no benefit since the result would be always the same regardless of the position and the mass of the other object. The formula would be useful neither to compute the force between two objects of finite mass nor to compute their motions.

If an infinite mass object were to exist, any object of finite mass would be attracted with infinite force (and hence acceleration) by the infinite mass object, which is not what we can observe in reality.

This point of view does not mean that infinity cannot be used in physics. For convenience's sake, calculations, equations, theories and approximations often use infinite series, unbounded functions, etc., and may involve infinite quantities. Physicists however require that the end result be physically meaningful. In quantum field theory infinities arise which need to be interpreted in such a way as to lead to a physically meaningful result, a process called renormalization. One application where infinities arise is the quantification of thermodynamic temperatures.

However, there are some currently-accepted circumstances where the end result is infinity. One example is black holes. Physicists have verified that, when a star experiences gravitational collapse, it will eventually shrink down to a point of zero size, and thus have infinite density. This is an example of what is called a mathematical singularity, or a point where the laws of mathematics, and therefore of physics, break down.

Re: What happens when.........


"immovable object" would refer to an item which you are basing all movement relative to.

"unstoppable force" is everything and anything; energy in motion never seizes and will pass infinitely through things(hypothetically)

therefore: Everything else would move