If you have 2 iron spheres and a magnet, the lighter sphere will move first to the magnet. But with earths gravity fall tests we know that every object falls with the same speed when dropped no matter theirs weight. What makes it different?
In: Physics
I don’t think there is a true ELI5 explanation for this, in part because this thought experiment needs refinement. Here are a few things to consider.
Forces are what cause an object to accelerate or decelerate (aka change velocity).
It is understandable why someone would say “every object falls with the same speed when dropped”. But a more accurate statement is that they experience the same acceleration due to earth’s gravity.
If you are at home and drop an object from standing height, the only significant force on that object is gravity acting downward. (Until it hits the floor and the floor pushes back to change its velocity to zero).
In your example of two iron spheres and a magnet you have probably imagined all three resting on a horizontal surface like a table. While both spheres will move toward the magnet, the heavier sphere may experience slower acceleration than the smaller sphere. This is because it experiences greater friction against the table and greater rotational inertia (search the definition of “inertia”) before it begins rolling.
The important point here is that the free fall example only involves the force of gravity. The magnetic objects example actually involves multiple forces – magnetism, gravity, friction – acting in multiple directions and axes. So these two situations actually cannot be compared as a basis for answering the question that you asked.
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