Questions tagged [free-fall]
Free fall is any motion of a body where gravity is the only force acting upon it. In general relativity, where gravitation is reduced to a space-time curvature, a body in free fall has no force acting on it.
87
questions
269
votes
11
answers
67k
views
Don't heavier objects actually fall faster because they exert their own gravity?
The common understanding is that, setting air resistance aside, all objects dropped to Earth fall at the same rate. This is often demonstrated through the thought experiment of cutting a large object ...
- 2,936
29
votes
7
answers
240k
views
Why do two bodies of different masses fall at the same rate (in the absence of air resistance)?
I'm far from being a physics expert and figured this would be a good place to ask a beginner question that has been confusing me for some time.
According to Galileo, two bodies of different masses, ...
- 409
65
votes
10
answers
40k
views
Why does a free-falling body experience no force despite accelerating?
Note: For the purposes of my question, when I refer to free fall assume it takes place in a vacuum.
From my (admittedly weak) understanding of the equivalence principle, falling in a gravitational ...
- 753
7
votes
1
answer
3k
views
Radial fall in a Newtonian gravitational field [duplicate]
Suppose an object of mass $m$ starts at rest at a radial distance $ r_0$ from a perfectly spherical mass $M$ (where $m << M$), $r_0 > R =$ radius of $M$.
Can we analytically determine when ...
- 885
25
votes
8
answers
29k
views
Would it help if you jump inside a free falling elevator?
Imagine you're trapped inside a free falling elevator. Would you decrease your impact impulse by jumping during the fall? When?
user145
7
votes
3
answers
10k
views
Calculating gravity when taking into account the change of gravitational force
This is a problem that has bothered me for a couple of weeks now, and I can't seem to wrap my head around it and understand it.
Let's say we have a planet with a mass of $m$. We also have an object of ...
- 164
1
vote
4
answers
7k
views
Time taken for object in space to fall to earth
The Problem
For a small mass a distance $R_i$ away from the center of the Earth, how long would it take for the object to fall to the surface of the Earth, assuming that the only force acting upon the ...
- 217
3
votes
4
answers
35k
views
Calculating impact force for a falling object? [closed]
Good evening, I'm trying to calculate what kind of impact force a falling object would have once it hit something. This is my attempt so far:
Because $x= \frac{1}{2} at^2$, $t=\sqrt{2x/a}$
$v=at$, ...
- 155
3
votes
1
answer
1k
views
Do free falling observers see gravitational blueshift? [duplicate]
Observers at rest in gravitational fields will see infalling light signals as blueshifted. Do inertial observers in free fall in a gravitational field see the same shift? If someone is standing on a ...
- 2,467
13
votes
1
answer
3k
views
From how high could have Felix Baumgartner jumped without disintegrating like a shooting star?
Today Felix Baumgartner jumped from 39 kilometres high and reached the earth safely.
Just considering friction, from how high can a human jump?
I expect that from a certain height, he would have ...
- 231
2
votes
4
answers
28k
views
Free falling of object with no air resistance [duplicate]
Why does an object with smaller mass hits the ground at same time compared to object with greater mass? I understand the acceleration due to gravity of earth will be same but won't the object with ...
- 151
3
votes
2
answers
257
views
Are time and gravity affected when at rest compared to free fall?
A falling object moves along a geodesic path ('straight path') in spacetime. When it comes to rest it now follows a 'curved path' through spacetime. Is the passage of time and force of gravity ...
- 185
2
votes
3
answers
5k
views
Deviation of free falling objects (Coriolis effect) using conservation of angular momentum
I read this pdf on non inertial frame, in particular I have a question on the deviation of free falling object due to Coriolis effect.
Consider a ball let go from a tower at height $h$. The ...
- 2,587
40
votes
6
answers
16k
views
Which ball touches the ground first?
This is a very well known problem, but I can't find an answer in the specific case I'm looking for.
Let's consider two balls :
Ball 1 weighs 10 kg
Ball 2 weighs 1 kg
Balls have identical volumes (so ...
- 503
13
votes
6
answers
9k
views
Is the Moon in a "Freefall" Around the Earth? [duplicate]
The force of gravity keeps our Moon in orbit around Earth. Is it correct to say that the Moon is in “free fall” around Earth? Why or why not?
I think the answer is yes. The moon is falling towards ...
- 243
5
votes
5
answers
9k
views
Can a balloon float into space? (+orbital velocity)
After watching the recent "space jump" a question arose. Why can a balloon not float into space? Can one be made/designed to do this?
Next, everything in orbit is falling back to earth. It only ...
- 158
2
votes
3
answers
2k
views
Acceleration due to Gravity: Free Fall [duplicate]
If we are in a free fall which implies we are accelerating at 9.8 m/sec every sec. And let's say that we are falling into a pit that has enormous depth. So isn't this be possible that we may ...
- 21
60
votes
6
answers
9k
views
Can a Skydiver Land On a Large Slide and Survive?
Please forgive my lack of artistic ability, but here's my question:
Consider that a skydiver, without using his parachute, were to fall exactly parallel to a giant curved slide that starts at $90\,^\...
- 706
52
votes
5
answers
28k
views
Freefall into snow
In the movie Frozen, the following dialogue takes place:
Anna: "It's a hundred-foot drop."
Kristoff: "It's two hundred."
Anna: "Okay, what if we fall?"
Kristoff: "...
- 1,147
41
votes
6
answers
70k
views
Could someone jump from the international space station and live?
Felix Baumgartner just completed his breathtaking free-fall skydiving jump from $120,000\,\text{feet} = 39\,\text{km}$ above the Earth, breaking the speed of sound during the process.
I was wondering ...
- 626
36
votes
5
answers
431k
views
Jumping into water
Two questions:
Assuming you dive head first or fall straight with your legs first, what is the maximal height you can jump into water from and not get hurt?
In other words, an H meter fall into water ...
- 2,060
19
votes
7
answers
6k
views
Does a long vertical pole fall at a different speed than a short vertical pole?
The formula for a falling object has $r^2$ in the denominator. This would mean that an object that is higher up falls more slowly than the standard $9.807\ \mathrm{m/s^2}$ that we are taught in high ...
- 4,567
15
votes
4
answers
9k
views
Water pressure in free fall
The increasing water pressure as you go deeper is generally explained in terms of the weight of the water column above the observation point pressing down. The question, then, is what would happen if ...
- 8,456
14
votes
7
answers
14k
views
Gravity - What happens when two objects of unequal masses fall freely towards the ground? (Revisited)
The common perception regarding what happens when two objects of equal sizes but unequal mass are allowed to fall freely towards the ground is that - both the objects make contact with the ground at ...
- 445
12
votes
4
answers
2k
views
Behavior of a loose coin on a free fall ride
At Six Flags over Texas, there used to be a free-fall drop ride called "the cliffhanger". Simply put, you got into a metal box, got elevated up to about 75 feet or so, and got dropped ...
- 1,427
8
votes
2
answers
895
views
Equivalence principle and radiation from falling particle
I am currently having a hard time solving a problem of GR from Lasenby's book.
I can't make it more clear than by quoting the exercise:
7.2 A charged object held stationary in a laboratory on the ...
- 2,916
8
votes
4
answers
1k
views
What does it mean that a falling mass in space doesn't sense any force?
I heard someone explain that if you were falling in space (i.e, a rooftop) you wouldn't sense gravity as a force acting upon you. But it would accelerate (≈ 9.8 m/s^2)
, which to me suggest that a ...
- 320
7
votes
1
answer
657
views
An example of a theory that respects the Weak Equivalence Principle but violates the Einstein Equivalence Principle
The Weak Equivalence Principle has any one of the following forms:
the inertial mass is equal to the gravitational mass
there exists a preferred class of trajectories through spacetime, known as ...
- 3,183
5
votes
3
answers
10k
views
Acceleration of an object dropped inside an accelerating elevator
A stone is released from an elevator going up with acceleration of $g/2$. What is the acceleration of the stone just after the release?
The answer is $g$. Shouldn't the stone carry the acceleration ...
- 1,406
4
votes
3
answers
907
views
Infalling light signals seen by a free falling observer
In this question/answer Does someone falling into a black hole see the end of the universe?, it is stated that an observer free falling toward/into a black hole will not see the end of the Universe ...
- 2,467
4
votes
3
answers
2k
views
Free Fall with Air Resistance
Can somebody help me understanding why when free falling the force on the vertical axis is F= -mg-kv, where k is the constant of air resistance and v the velocity?
Suppose the vertical axis is ...
- 247
3
votes
2
answers
647
views
Does GR imply a fundamental difference between gravitational and non-gravitational acceleration?
Does the equivalence principle imply that there is some fundamental difference between acceleration due to gravity and acceleration by other means (because there is no way to 'feel' free fall ...
- 2,467
2
votes
1
answer
142
views
How does instantaneous velocity cause displacement in just one point? [closed]
I have a question.
Falling object graph is curve shape right?
And instantaneous velocity is tangent line but how does this velocity make displacement in distance? Because suppose instantaneous ...
- 311
2
votes
3
answers
555
views
Why can't we think of free fall as upside down rocket?
/\
/ \
| |
| m |
| |
------ <--- floor (Rocket A)
This rocket is accelerated (g) upwards then mass(m) falls on the floor.
...
- 5,619
2
votes
3
answers
435
views
Gravity and bottomless pits [duplicate]
Assuming that someone is theoretically able to make a hole through the center of a large planet, and then jumps down the hole, what will happen? Given my understanding of gravity and energy, my ...
user38735
2
votes
3
answers
9k
views
Galileo's law of odd numbers
The Galileo’s law of odd numbers states that the distances traveled are proportional to the squares of the elapsed times. In other words, in equal successive periods of time, the distances traveled by ...
- 179
1
vote
1
answer
438
views
Is the radial two-body problem solvable?
Is the radial two-body problem solvable, i.e. does the differential equation $$r''(t) = 1/r(t)^2$$ have an analytic solution? If it does, what is the solution? And if not why does everyone say that ...
- 117
1
vote
2
answers
2k
views
Force on carabiner from free fall [closed]
Suppose I weigh about $75~\text{kg}$ and I am attached to a (non-elastic) rope which is attached to a carabiner which can take at least $20~\text{kN}$. Suppose furthermore that I reach terminal ...
- 173
1
vote
1
answer
1k
views
How to obtain the distance traversed by a free falling body equation?
I know that the distance that a free falling body has traverse through time is given by $d=0.5*g*t^2$. I would like to know how to get to this equation to study a bit more how it was obtained. I have ...
- 123
1
vote
1
answer
1k
views
Does mass distribution/center of mass affect free fall?
An everyday is example would be cars. If you were to drop a car, not taking air resistance into account, would a front-heavy car tumble forward as it fell? And a car with a perfect 50/50 front/rear ...
- 11
-2
votes
1
answer
237
views
What consequences would it have to postulate zero shift vectors in GR?
The shift vector is a part of the metric tensor in General Relativity (GR). It's $g_{0i}$ with $i$ in $[1,3]$.
This post is related to this question. There, I ask whether a changing of coordinates is ...
- 103
-4
votes
1
answer
248
views
Ascertain the height an object has fallen from given force exerted and mass [closed]
An object of a given mass falls from an unknown height. If the force exerted by the object on contact with the ground is known, how would you ascertain the height from which the object fell?
- 185
34
votes
7
answers
3k
views
Cause of weightlessness [duplicate]
I'm a first year engineering student who is new to physics, so I apologize if my question is stupid. But in our statics course we are using the book "Engineering mechanics: statics" by R.C. Hibbeler ...
- 359
21
votes
9
answers
13k
views
Does the weight of an hourglass change when sands are falling inside?
An hourglass H weighs h. When it's placed on a scale with all the sand rested in the lower portion, the scale reads weight x where x = h.
Now, if you turn the hourglass upside down to let the sand ...
- 323
13
votes
4
answers
29k
views
Force of an impact on water
Today, at the Brazilian news, I heard that a men fell from a cruise into the sea, from a height of 50m, and decided to see if he could have survived. I took his weight for being 80kg.
I did $V^2=V_0^...
- 483
6
votes
1
answer
7k
views
Coriolis force in free fall
Does the coriolis force has any measurable effect in free fall from large heights?
Take for example the sky diving experiment by F. Baumgartner who started from a height of about 40 km above New ...
- 1,692
6
votes
1
answer
342
views
Temperature of Bose-Einstein-Condensate in space
Recently I heard a talk by Bill Phillips, who talked about the coldest temperatures in the universe.
Among others, he sayed that the coldest temperatures created at the moment are BECs, which can ...
- 759
5
votes
2
answers
744
views
I know that free fall in vacuum is independent of mass. But what happens in air?
Pardon me if this sound somewhat trivial to some of the highly qualified users here.
So I know two objects will fall at the same rate if they are in absolute vacuum, so what I'm assuming is that the ...
- 153
4
votes
2
answers
746
views
Change of velocity of a falling object over height (acceleration changing with height)
I've been trying to solve this by myself without success. I am trying to find the velocity of a falling object as its height varies (change in velocity as it falls). Although it is often assumed that ...
- 45
4
votes
7
answers
2k
views
Why a falling object has a constant acceleration?
My question is could we derive the fact that a falling body has constant acceleration from Galilean relativity and only?
There is an answer on this site which claims this (accepted answer on the ...
