We don’t have any documented proof about a condition when an unstoppable force charged with infinite energy meets an immovable object which is not charged with boundless energy. 

In fact, this is a hypothetical case of science. This is more so as we don’t have records of this situation or case ever happening. In other words, it has never happened.

Immovable Object 5e Means

A stationary, unyielding force or object. I was sitting in the car, immobile and alone, as I watched her walk away.

An unstoppable force meets an immovable object

On examining the velocity or speed of an object, we find that there is nothing that cannot be stopped or made to stop due to circumstantial conditions. As a result, when such an object hits an immovable object, its speed or velocity comes to an end. 

When a bullet is fired, this object stops losing its velocity or speed on hitting an immovable object be it a wall or tree. The immovable item, when hit by an unstoppable force, does not change its position or location. 

For all practical purposes, we can say this is an academic subject relating to velocity or speed. But in reality, there is no unstoppable force that cannot be stopped with physical counter-force. Hence, this is a hypothesis. 

What happens when an unstoppable force meets an immovable object?

Totally paradoxical in nature, the skepticism is raised on the scientific ground that nothing practically can be unstoppable. Hence, the issue of an immovable object being hit by an unstoppable force just does not arise, at all. 

In fact, the basic doubt about the veracity of this arises out of the fact that how an object can be unstoppable? Even if the object is excessively powerful, charged by infinite electricity or power or force, it would stop when it hit an immovable object. 

In such a case, that unstoppable will lose its strength or speed on hitting or colliding with an object which is stationary or standing in one position, say a mountain, a tree or a house. The speed of the object will end in such a case of collision. 

Unstoppable force: A hypothesis of Science

Here the aspect of the mere hypothesis of an object being unstoppable due to its inherent force comes to light. As a theory of science, it seems improbable. This is more so as we don’t have any recorded example of it.  

Till now, we find all objects moving at a tremendous speed lose its velocity on hitting an immovable object. This is more an academic issue to study velocity in its real perspective than a reality.  

The primary reason for it, as explained above, is the fact that no object around the earth is unstoppable. Everything can stop when its inherent energy or electricity comes to an end. To exemplify, an aircraft or moving car would come to a stop when its fuel exhausts. When it collides with an immovable object, the movable object will destroy and come to an end with its speed getting zeroed.  

This is the normal theory of all speeding objects. We don’t have any historical evidence to suggest that an unstoppable force (other than planets in the galaxy moving on their axis and orbit with tremendous force that cannot be stopped) ever existed in any man-made scientific form.

In fact, an object is made to move or acquire speed or motion with the addition of external force, power or pull. But the force will lose its intensity if the movement of the external force or pull is stopped. It will no more be a moving object with speed. Subsequently, the question of an object being unstoppable does arise at all. 

In Conclusion:

To conclude, we can say velocity depends on external force. It is this external force that adds speed to an object. But this object cannot move eternally. Its speed will come to an end once the external assistance like fuel in the case of cars is exhausted. Hence, this is a purely hypothetical issue that hardly has any answer with scientific base.