# Confusion with free fall

• B
tomlib
Hello. I read on Wikipedia that when a body is in free fall from zero mass, its mass does not matter and two bodies of different weights will fall at the same speed. I think this is not correct. If I consider that the bodies are in a weightless state and the gravitational force will act on them. This force will be as great as the weight of this body.
If a greater force acts on something, it will most likely move faster. Is my reasoning correct?

Homework Helper
Gold Member
The problem is that no force or weight can be measured during pure free fall.
If you could use a measuring device, the fall would not be free.

Mentor
Can you link to the specific page in question? It seems like you may be misremembering the quote.

Homework Helper
Gold Member
Galileo presumably did an experiment in the late 16th century in which he dropped two objects of different weight from the top of the tower of Pisa and found they reached the ground below at the same time. Unfortunately there is no video of it. However, US astronauts repeated Galileo's experiment on the Moon and made a recording. They dropped a feather and a hammer through the airless space above the surface and verified that Galileo was right when the feather and the hammer hit the ground at the same time.

vanhees71 and Lnewqban
If a greater force acts on something, it will most likely move faster. Is my reasoning correct?
What is the relationship between force and acceleration? (Hint: F=ma). So, while the mass influences the force of gravity, it also influences the acceleration. If you write out the force due to gravity, and also the acceleration you will see, the mass "cancels out."

EDIT
I read on Wikipedia that when a body is in free fall from zero mass

I'm not sure what "... from zero mass" means.

Last edited:
Dale, vanhees71 and russ_watters
tomlib
https://cs.wikipedia.org/wiki/Volný_pád

I think zero mass means the zero begin speed. I use translator.

I don't know much about the formula and I don't exactly understand the shortening in the article. The formula and reasoning must be wrong. It is clear that when I say that as force increases, acceleration must also increase. Strength increases with body weight. If I push the car with more force it will move faster. Again, a place is offered here for the description of such a phenomenon, i.e. the necessary initial force,
the fact of measuring speed and force. Free fall could be measured on video, but it is difficult to test it somewhere. It seems to me that a=F*m, where g is substituted for F.

Homework Helper
It seems to me that a=F*m, where g is substituted for F.
Not exactly. ##F \neq g##$$F_\text{gravity} = mg$$The force of gravity on an object increases when you increase gravity. It also increases when you give the object more mass.

But we also know that$$\sum F=ma$$If gravity is the only force operating then ##\sum F = F_\text{gravity}##. So$$a = g$$.

PeroK and russ_watters
diogenesNY
At the risk of pointing out the obvious, this is an extremely easy proposition to experiment.

Just drop two reasonably compact items of meaningfully different masses: off a ladder, second floor window, the front porch, whatever. Great accuracy in measurement should not be needed, just make sure that there aren't hurricane force winds present, and that object B is about 3 or 4 times the mass of object A. Repeat several times. Have an assistant near the landing zone to watch the impacts just to be sure.

Should give you all the working data (within a reasonable range of accuracy) that you need.

Dale and Lnewqban
zanick
Hello. I read on Wikipedia that when a body is in free fall from zero mass, its mass does not matter and two bodies of different weights will fall at the same speed. I think this is not correct. If I consider that the bodies are in a weightless state and the gravitational force will act on them. This force will be as great as the weight of this body.
If a greater force acts on something, it will most likely move faster. Is my reasoning correct?
i think what was said in more technical terms, is that yes, you have more "force" due to a higher weight (which is a force) but the mass is greater, so it cancels out. 9.8Newtons on a 1kg object will accelerate at 9.8meter/sec/sec (acceleration). since acceleration (g) is constant, if increase the mass to 2kg, that will raise the weight of the object to 19.6Newtons, and the acceleration is still 9.8mpsps......... later you can investigate why the object is weightless when it falls, but still accelerates with respect to the ground..... hmmm it seems the ground is accelerating up to the object.... see Einstein and the bending and warping of space time as a cause.