Saturday 26 October 2019

newtonian mechanics - Why do things accelerate?



Why do things accelerate? Let's say you are pushing an object in space for example, why would the object accelerate? I know that when a net force acts on an object, it accelerates but that is my question, why does this happen? Why wouldn't the velocity stay the same with a net force acting on an object?Because isn't it the same force? I'm trying to figure this out and it's making me crazy! EDIT: I changed the scenario because what i'm asking has nothing to do with gravity



Answer



Many sciences are a posteriori, and physics, the study of nature, attempts to form theories and models through induction. We observe stuff, we take data, and we try to come up with generalizations. The fact is, we aren't really sure if such generalizations exist or not. We simply belief so, because it makes life easier, and so far this belief has not been shown wrong.


Back to your question: why do things accelerate? This is a question that might never be answered. What physics is doing is trying to answer how things accelerate, or become hot or cold, or increase or decrease in mass. The reason why "truths" from the past are no longer true today, and "truths" today may very likely be no longer true some day, is that we are going bottom up, instead of top down: we can only see the manifestations of those generalizations, if they do exist, and we are doing nothing more than guessing what they are.


Imagine an alien seeing an Earth person pressing gas pedal, then the car moved. The alien never saw the interior of a car, and when she went back, she theorized that some mechanism makes the action of pressing gas pedal move the car. After 1 million observations of this correlation and none of them showing anything that contradicts her theory, she was so sure that pressing gas pedal will lead to the movement of the car.


But, she does not really know what kind of mechanism it is, that is hidden inside the car, that makes this theory valid. Although her theory is sound, as pressing gas pedal will 100% lead to the car moving (given the right conditions), she has no idea why, and she can never find out why if she is unable to disassemble a car and see for herself what is within.


We are aliens, and nature is the car. The sad thing is, we might never have a chance to see what's within the car. All we can do is observe, theorize, and use these theories to make our lives easier.



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