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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.

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Do objects really "fall" at the same rate? [duplicate]

I understand that a hammer and a feather were dropped on the moon and they both landed at the same time. I understand that for all practical intents and purposes all objects do fall at the same rate. ...
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Can two objects of different mass experience the same air resistance? [duplicate]

This question is assuming that the objects have the same shape and size, but different masses. I know that all objects have the same gravitational acceleration on earth, which is about 9.8 m/s^2. ...
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How could I calculate the time it will take for light and mass to go towards a black hole and come back, to and from constant radial distances?

If you have a "perfect mirror" and a "perfect trampoline" at some constant distance outside a black hole's event horizon: a) How would a shell observer at some distance farther ...
Zach's user avatar
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Equation for the curve of a free falling particle in Kruskal diagram

I'm currently trying to help a friend who is taking a GR course (she is an experimentalist, and I'm rusty as hell, please be patient). We got stuck in an issue concerning Kruskal coordinates. We are ...
André Noronha's user avatar
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2 answers
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Gravitational attraction between two bodies and gravitational accelaration [duplicate]

Since Newtons laws on gravity state that the gravitational attraction between two bodies is directly proportional to their masses and inversely proportional to the square of the distance between them, ...
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Necessity of equivalence principle

Is the equivalence principle necessary to formulate general relativity or is it possible to formulate general relativity without it?
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Definition of free fall in GR

I apologize if this question is very elementary. Somewhere I've found the following: Freely falling observers (resp. photon) move on timelike (resp. null) geodesics. Please note that by definition, ...
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Question regarding projecticle in freefall disregarding air resistance [closed]

This question is regarding the following problem A stone is thrown up from the top of a tower 20 m with a velocity of 24 m/s at an elevation of $30^\circ$ above the horizontal. Find the horizontal ...
koiboi's user avatar
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Why will a cylinder tend to freefall on its side?

In a video I saw about the U.S. military’s idea “Rods from God”, it said a uniform steel cylinder will tend to freefall in the air on its side if not corrected. It won't freefall vertically if left to ...
Wyatt's user avatar
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Why do objects with more mass fall at a faster rate (factoring in air resistance)? [duplicate]

My class had to do an online simulation about the different free fall times of objects, both on Earth and in a vacuum. In it, I noticed that in an atmosphere, objects with greater mass fell faster ...
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Couple on free falling rod [duplicate]

When free falling rod is punched at top then it would start rotating as shown below : But only force here is punch force so how does a couple form here? Gravity is present but isn't it along the axis....
Harjot Dhillon's user avatar
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Time taken for an object to fall [duplicate]

Time taken for an object to fall is generally given by $$t=\sqrt{\frac{2h}{g}}.$$ But this is only true under the assumption that gravitational acceleration is constant. With variable gravity what ...
Star Gazer's user avatar
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When doing Ice Skating, is it more painful to fall in motion or without motion?

Let's imagine I'm ice skating on a perfectly flat surface. In the first scenario, I am falling motionless. I expect my forces to looks like this: In the second scenario, I am falling with some speed, ...
Martin Magakian's user avatar
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Dropping a skyscraper (hypothetical question)

This is hypothetical question: imagine a tall skyscraper says 1000m tall is lifted by a nign indestructible cables attached only at the top of the building. When the cable is released what happens? ...
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Does it takes more or less effort to dribble in a micro-$g$ environment?

Imagine an astronaut is practicing with a standard official basketball on an orbiting space station. Assume everything is in free fall so I wonder would it consume less or more effort to dribble ...
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What would happen if I swirl a bottle of water in the space station?

Right now I am swinging a bottle of water in a tight circular motion to form a vortex, the vortex will last quite a while after I stopped swinging it. The vortex will took the shape of a funnel in 1g ...
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Throwing a pencil up in an elevator speeding upward

The classic question is "What happens to a pencil if I, standing in an elevator speeding downward, lets go of it at the exact second the elevator begins its fall?" As I understand, the ...
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Einstein equivalence principle conflict

The weak principle of equivalence says that freely falling towards the Earth is the same as being in space far away from any stars. However, imagine that you are freely falling on a planet with $g=9\...
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How to derive the equation of motion of a test particle free falling into a Schwarzschild blackhole from distance $R$? [closed]

This answer gives the equation for $t(r)$ without the derivation. I have found the derivation for particles free falling from infinite distance using the Schwarzchild metric and Lagrangian, but I don'...
John Ao's user avatar
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Shouldn't all things falling into a black hole meet at the horizon?

Consider two observers starting to fall toward a black hole from rest at different distances from the black hole with their worldlines shown on the Kruskal-Szekeres chart below On the diagram, it ...
Chris Laforet's user avatar
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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 ...
MartyMcFly's user avatar
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Why does gravity cause objects to pull other objects with constant acceleration and not constant force? [duplicate]

I know that this may come off as an incredibly dumb question, but please hear me out for a while. Why don't objects just tug at other bodies with a constant force? Instead, why do they apply ...
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4 answers
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Is it easier to hit a ceiling of an elevator with a jump if the elevator is in the free fall?

In contrast to a popular question, here I want to hit a ceiling of an elevator. If the elevator is standing still, my legs are not strong enough to generate a jump that will help me hitting the ...
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So I've found out heavier objects technically do fall faster? [duplicate]

Given the Earth's mass to be $M_E$, I know that $F_G = -\frac{GM_Em}{d^2}$, so the gravitation acceleration of a mass towards Earth is $g = -\frac{GM_E}{d^2}$. But what about the force exerted by the ...
Ibrahim Nadeem's user avatar
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Why free fall motion is parabolic?

Consider no air resistance. If we throw a ball vertically upward from my point of view it goes vertically up and down and moving along straight line. But from point of view observer in outer space it ...
123's user avatar
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Ground force on free falling object [closed]

Let a body be falling freely from height $h$ to the ground. Can we express the reactionary force $F$ acting on the body from the ground as a function of $h$, i.e. $F=F(h)$? (My attempt contains also ...
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Defining Free Fall: Does Gravity Need to be the Sole Force Present?

Can a scenario be considered free fall in physics if the work done by forces other than gravity is zero, but those forces are still present? Or is it necessary for gravity to be the only force present ...
Authentic Melody's user avatar
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4 answers
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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 ...
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Differential equation of an object dropped from certain height

I want to solve this problem - A ball of mass 2kg is dropped from a tall building with zero initial velocity. In addition to gravity, the ball experience a damping force of the form -2v, where v is ...
Dinesh Katoch's user avatar
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Is the sensation of falling purely due to air resistance?

When I jump off of something, even with eyes closed I can be pretty certain that I'm falling due to the associated sensation of falling. However, as gravity should be affecting each of my internal ...
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6 answers
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How does unbalanced force ever create? [duplicate]

This question rather seems elementary but has been bugging me for a while! How does even unbalanced forces create? The main driving force of this question is Newton's third law Let's take Free Fall: ...
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Ways of losing energy of a bouncing objects in vacuum other than Heat and Sound

When we released a bouncing object in a vacuum chamber, the object will fall, contact the ground of the chamber and bounce back up. We know that the object will not return to its original height ...
Koh Yi Min Jason's user avatar
2 votes
1 answer
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Why won't a pen work on the International Space Station?

Today, in my physics class, we were discussing the effect of microgravity (specifically on the ISS) on various objects of everyday value. I learnt that a normal pen wouldn't work in space (So they ...
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Derivation of Proper Time of Fall in Schwarzschild Metric

Some time ago, in this question (Proper Time of Fall in Schwarschild Metric), I asked how to find the proper time of fall of an observer in the Schwarzschild metric because I had found many different ...
Vinicius Araujo Ritzmann's user avatar
1 vote
1 answer
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Does weightlessness make no difference to free fall?

I looked up a lot of articles and questions about free fall motion and weightlessness. And I know there are a lot of similar questions. In conclusion, I understand that there is no way to distinguish ...
NOH WHIREA's user avatar
2 votes
1 answer
147 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 ...
Heroz's user avatar
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If a ball experiences a force when it hits the ground, why can we still use the kinematic equations to solve for its freefall time?

Suppose a question states: A ball is dropped from a height of 2m. Find the time it takes for which the ball is in free fall. To solve this, we would plug in our known values into the kinematic ...
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2 votes
0 answers
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Frame of reference of a freely falling observer in General Relativity

Suppose I have an Einstein manifold (a manifold with a metric that solves the Einstein field equations. We can take $\Lambda = 0$ for simplicity in this example). The worldline of a freely falling ...
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1 answer
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Can a gravity-compensated accelerometer still measure or detect free-fall?

Take the simplest example of a plane aligned perfectly to the NED inertial reference frame at all time. The plane is restricted to only thrust or elevate upward or down with zero pitch, yaw, and roll (...
KMC's user avatar
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0 answers
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Equation for position and velocity of a body falling in a gravitational field [duplicate]

I have tried asking this question on many forums and have so far failed to get a clear answer. Here is the problem. A body with a negligible mass is falling from a distance $R_1$ in a gravitational ...
Iam Cleaver's user avatar
1 vote
2 answers
77 views

Why is it proclaimed for astronauts to be "falling"?

My physics teacher explained that the reason why it looks like astronauts are floating is because they are "falling". However, the way I think of it is that the outwards inertial force of ...
Am0000's user avatar
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2 answers
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If you drop a coin inside a car that is slowing down, where will the coin fall?

If you drop a coin inside a car that is deccelerating, where will the coin fall with respect to the vertical where you dropped it? My thoughts where since it still has a velocity forwards, even ...
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Body free fall calculation of the time durance as a direct derivation by time (non-relativistic)

Let's assume a body in free fall during 16 meters without resistance and I'd like to directly calculate the time of this fall. Sure, one could painfully calculate: $v^2 = 16 m·9.81 \frac{m}{s^2}$ $v = ...
Marcus's user avatar
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2 answers
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What is the weight of a body during free fall?

Is it '0' or is it equal to the product of the mass of the body and acceleration due to gravity? Please explain in relation to weightlessness of body in freefall.
Bighnesh's user avatar
4 votes
3 answers
255 views

Could you feel your weight falling through the a tube drilled through the center of the earth?

Suppose you drill a hole through the center of the earth (assume the earth is uniform and no air resistance) and you jump in. Would you be "weightless" throughout the entire fall? The reason ...
Curiosity's user avatar
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3 votes
1 answer
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How are objects kept free falling in the LISA experiment?

I'm watching a video about the LISA experiment, which will be used to detect gravitational waves. In there, three space stations will be launched and will follow the Earth in its revolution around the ...
robertspierre's user avatar
3 votes
2 answers
162 views

Are all objects freefalling at the same rate inside a black hole?

We know the phrase "all objects move at the same rate when freefalling regardless of their mass" (interestingly this isn't even true because the objects are exerting their own gravity, but ...
Árpád Szendrei's user avatar
2 votes
1 answer
77 views

"Outrunning pressure": Liquid in free-fall

I've checked out related questions and didn't see an answer to my question. Scenario: Liquid in open-top container, together accelerating downward with magnitude $g$. It was straightforward for me to ...
electronpusher's user avatar
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If I dropped a golf ball straight down from about 5 meters, would air resistance cause a noticable change in the acceleration of the ball?

I am working on a Grade 11 physics lab report. I dropped a golf ball from a balcony 5m and 13cm off the ground. When I did all the calculations, the acceleration was 7,72m/s (calculations below). I am ...
rootbeer2017's user avatar
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2 answers
178 views

Speed of falling objects / with different altitudes

I have a question about gravity So as we know gravity is significantly less on high mountains or tall buildings and increases as we lose height ☕ My question is that if we have 2 objects with the same ...
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