Do the 'feather' and 'hammer' really fall at the same rate?

Question

If someone asked me why the planet this 'feat' was performed on doesn't follow the same 'rule' I wouldn't know what to say. We're left with the impression the masses in general are irrelavant. In other words if mass is irrelavant, why is there not the same displacement of the earth or moon (where ever this trick is done) in the direction of the feather and hammer?

thanks hznfrst...

Answer 1

Try the following experiment, Take a pool ball and a sheet of paper, and drop them together from the same height. One will reach the ground much sooner than the other. Which one?!

Now screw the paper up as tight as possible, so that it's the same size as the pool ball. Once again, drop the screwed up paper with the pool ball from the same height. Can you now see ANY difference in the times at which they hit the ground?!

If THAT doesn't convince you of the relative importance of air resistance on light, very extended objects, nothing can. Once the air resistance is minimized, objects fall at essentially the same rate; in a perfect vacuum, they fall at IDENTICAL rates.

But ponder one more point: Why do you think that birds' wings consist of many spread-out feathers rather than packed-together pool balls? It's because by BEATING those extended feathers on the air, the resistance now provided by the air gives lift to the birds!

Live long and prosper.

LATER EDIT: The absolute equality of "gravitational mass" and "inertial mass" is a "mystery" in Newtonian physics, but a NECESSITY in Einsteinian general relativity. That is because gravitational motion is seen in relativity as a purely kinematical property of the geodesics of spacetime. (This independence of gravitational motion on mass is known as the weak equivalence principle.)

"Eotvos" experiments (named after Baron Eotvos of Hungary, who first performed such experiments in 1889) attempt to measure whether these two masses are identical (or equivalently, test whether the weak equivalence principle is satisfied). They have even been performed in recent decades on different isoptopes of the same element, to see whether possessing different neutron/proton ratios has any effect. The equality of the two masses tested this way has been found to exist with errors of order only 10^(-12).

If you're a committed and anti-relativistic Newtonian, results like this might deepen the mystery and lead you to seek an "explanation" for the apparent equality of the "two kinds" of mass. However, relativists can view the same experiments as confirming one of the basic tenets of general relativity --- that all masses follow the same kinematical geodesics, whatever those masses are, or what they are made of.

Answer 2

Mass does cancel out in acceleration due to gravity.

The hammer and the feather will fall at the same rate on any planet IF there is no atmosphere to interfere. They are both accelerated by gravity the same, but the feather has much more drag and develops much less momentum for the same speed.

If you get a big tank and pump the air out of it, then go inside with a space suit (so you can breathe) then when you drop a feather and a hammer at the same time from the same height they will hit the floor of your tank at the same time.

You can do a simpler test by dropping a penny and a whole sheet of typing paper. Watch the paper sail and drift down and the penny will win the race to the floor. Now crumple the paper as tightly as you can and do the drop again. This time the paper and penny will hit at nearly the same time. If you could crush the paper such that it had the same air resistance as the penny, they would hit at precisely the same time.

Answer 3

Well, it was done on the moon by astronauts but can also be done on earth in a vacuum chamber.

In physics, there are two kinds of mass: gravitational and inertial. An object's gravitational mass makes it fall faster in a gravitational field, however its inertial mass makes it harder to change its motion, which slows it down by precisely the right amount so that all objects fall at the same rate.

Even now physicists aren't sure whether these two masses are distinct or not; they just have exactly the same magnitude, as if nature is messing with us just for fun.

Hey Dr Spock, there aren't any "anti-relativistic" physicists that I know of - are you kidding with that? But thanks for that explanation and reminding me of Eotvos.

Answer 4

Newton actually said "a guines and a feather". He was pointing out that gravity affects things equally, but air slows lighter things down as they fall.

Neil Armstrong demonstrated it was true on the moon with a hammer and a feather, and, what is almost unbelievably classy for the Yanks, the feather came from Grantham.

Answer 5

In a vacuum they will fall at the same rate. In the air the feather will float and the hammer will out accelerate it.

Answer 6

If that air tight space is a vacuum,yes.If there is air in there then the feather will succumb to wind resistance and fall much more slowly than the hammer.

Answer 7

Yes. Why yes they do. Get a hammer and a feather and drop them at the same time. Experiments rock!

Answer 8

Yes, they accelerate at the same rate (9.8m per second squared). In "real life" though, the hammer will fall first because of air friction playing a role in their velocities.

Answer 9

..sure,yes they fall at the same time in vacuum tube.But ancient age scientist Aristotles told that hammer was first.

Answer 10

in real life, no, hammer fall first, in a vaccum chamber, both fall in the same speed(gravity)