[Misconceptions About Falling Objects] (Viewer #816,152)
The part about gravity having to overcome inertia to accelerate the object is a point that often gets left out of the discussion.
Also left out: because of air resistance, a heavier object will hit the ground first. The effect isn’t noticable over a 5-foot fall, though.
Wait. . . . Any physicists in the audience?
Hervey’s right. Inertia never gets mentioned in the lessons I’ve been subject to.
It’s always “X and Y, no matter their difference in weight, will hit the ground at the same time if dropped from the Tower of Pisa. (Discounting wind resistance.)”
My question is: isn’t the effect of inertia overcome at some point? But of course by then it would be too late: if the bowling ball started with greater inertia, wouldn’t it stay permanently behind the volleyball when their rate of fall became equal, if they experienced the same wind resistance?
We’ve done well with NASA programs so far, so I assume scientists understand gravity excellently well. I now wish I did.
Gravity is a “body force.” It acts on each individual particle in a manner equal and opposite to the particle’s inertia (i.,e., mass and mass’s resistance to acceleration.) Therefore, it doesn’t matter how many particles you have (massive ball vs. a feather). Each particle is accelerated the same way.
One studies body forces not only in physics, but in structural and fluid mechanics and in other disciplines. -Jimmy (aeronautics & astronautics).
Stupid Oppo question. It sounds like Jimmy has a lifetime of knowledge in this field:
In a vacuum, wouldn’t any force (such as gravity) acting in a manner equal and opposite to the inertia of a particle cause a net acceleration or displacement of zero? Surely if I shove a refrigerator with a force equal to its inertia, nothing will happen.
Engineers have a standard reply when asked something and they don’t know what to say.
F = m a
and if you’re a professor, you write “QED” on the blackboard.
Your question is more aptly put (I suspect) as, “Why is the force of gravity depend on an object’s mass in EXACTLY the same proportion as the object’s resistance to acceleration (its inertial force)? I read articles occasionally where physicists admit they don’t know the answer.
“Surely if I shove a refrigerator with a force equal to its inertia, nothing will happen.”
But the refrigerator’s “inertial force” only appears as the “a” in “ma”, i.e., only when accelerated. As you push the refrigerator, your hands feels it pushing back. That push back is its inertial force.
One day when Walter Williams was guesting for Rush, he made a point about the nature of reality by saying that a chicken and a brick, dropped together, would hit the ground at the same time. I sent him an email and reminded him that it was only true if the chicken was dead.