Questions tagged [free-fall]

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How gravitational time dilation affects free-fall time

Consider a point-like planet having a large mass $M$ and two small point-like objects with masses $m_1<m_2$. Drop down each of them separately from distance $d$ on the planet, let $T_1$ and $T_2$ ...
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Velocity of bullet-block system

If a bullet is fired at a certain speed and hits (and is embedded on) a block at the edge of a cliff causing it to fall, will the initial velocity of the bullet-block system have any effect to the ...
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1answer
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The behaviour of acceleration of a ball in motion

I have a few doubts on how the acceleration of a ball works when we throw it up in the air, In my mind, I could imagine it in some different "real world" cases, So I am listing them all down,...
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1answer
55 views

Intuitive explanation for the second solution. Projectile problem [closed]

Take the classic problem of a person standing on a high building/cliff and throws an object which follows a parabolic path to the ground. Solving this problem gives two solutions for the time in which ...
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Stokes law, falling body problem: what sign?

This is quite a basic question, but it gives me just headaches, after I was really thinking about it: By equilibrium a falling body in a viscous medium will ultimately have the following forces ...
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Weightlessness and free fall on oil drop experiment

Suppose I have an oil drop which is negatively charged placed in a box with the bottom of the box negatively charged. When this box and oil drop is placed on a table where the box is stationary, the ...
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1answer
34 views

How no Contact forces on objects with stacked on top of each other

How can there be no contact force between two bodies stack one top of another during freefall if they are in contact?ho
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3answers
40 views

Free fall and contact force

If two bodies are stacked on on top of other and in free fall and there is no contact force how come they remain in contact ignoring drag. Secondly if two object were at rest say on table and table is ...
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1answer
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Contact force and intermolecular distance between two objects during free fall

I am a bit confused. When two objects are in a free fall such that when released to free fall they were one top of another, will there be any contact force between the two objects and will there be a ...
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2answers
63 views

The effect of pressure on the height of the first bounce of a volleyball [closed]

I'm currently working on an experiment and the first step is to come up with a hypothesis, which is based on a physics proof. The experiment involves droping a volleyball from a fixed height and ...
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Ridiculously large velocity: free fall, Stokes

According to free fall by Stokes law the terminal velocity is given by: $$ v_T = g\cdot\dfrac{m}{6\cdot r\cdot\pi\cdot \eta}$$ If you're talking about a chutist and use for air as viscosity $\eta = ...
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Does mass affect gravity? [duplicate]

I read somewhere that mass affects gravity– if the mass of the objects are larger, then the force of gravity between them is larger. So, does this mean that the gravity between 2 massive objects is ...
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1answer
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Free fall equations [closed]

I've been looking for this on the internet for a long time, but nowhere explains it clearly, and I need to explicitly calculate this and not other things: If I have the height at which an object is, ...
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Finding the time required for an object to move from point A to B when the Force exerted is a function of distance? (Proportional to the inverse sqr) [duplicate]

I know we will have to use double integration. But I need some help in making and solving the equation. The example of these scenarios is the time taken for an object falling towards Earth from ...
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1answer
48 views

State space of free falling object is time variant?

In the case of a free fall object, if $h$ denotes distance from floor and $v$ the speed, then, given an input $U = g$, and $X=[h \quad v]^T$ and $\dot{X}=[\dot{h} \quad \dot{v}]^T$, I found that the ...
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3answers
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Does material (density) affect falling rate of objects? [duplicate]

Suppose Galileo dropped a one-kilogram ball of cotton and one-kilogram ball of iron from the top of the Leaning Tower of Pisa, then which one will reach the ground first? Assume that the cotton ball ...
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1answer
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Does a experiment measured in free fall here on earth and inside a black hole gives the same result?

According to Einstein equivalence principle observer in free fall measure the same thing in experiment made in their laboratory frame. Let us take for example the probability $P$ of an hydrogen atom (...
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Is it possible to show simply using the Lagrangian that a body in free fall (& $v_i=0$) follows the most “ efficient” path ( i.e. a vertical line)?

In this video lecture by M. van Biezen ( Loyola Marymount Uni) https://www.youtube.com/watch?v=uFnTRJ2be7I&list=PLX2gX-ftPVXWK0GOFDi7FcmIMMhY_7fU9&index=2 it is shown how to apply the ...
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1answer
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Why don't we ever see astronauts on space walks adjusting their orientation by rotating their arms?

Why don't we ever see astronauts on space walks, or floating 'weightless' in the ISS, adjusting their orientation by rotating their arms like we do instinctively when about to lose our balance and ...
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2answers
60 views

Why does two objects with different weights fall at the same time, taking air resistance to be negligible? [duplicate]

For instance, since weight is given by mass x gravitational field strength and assuming both objects have the same gravitational field strength and the only changing variable is its mass, why do they ...
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2answers
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Is this general relativity diagram correct?

The following diagram is presented in my professor's general relativity notes: The diagram comes along with a description of the relativistic bending of light, and the explanation is somewhat clear, ...
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Does a slowed down version of small stone falling in water look the same as a big rock falling in real time?

I was wondering: If you let a small stone drop on a body of water, record it on film, and replay the scene in slow motion, will it be possible to see the difference with a huge rock that falls, in ...
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1answer
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Is there any formula to calculate the impact when falling onto water surface from speed?

So I know how to do the math of instantaneous speed when doing free fall: $$v = g \cdot t $$ and here comes into my question: how can I calculate the impact on water surface when hitting it at a ...
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1answer
81 views

Why do few droplets of rain fall a short time before a downpour?

What is the reason that before a heavy shower of rain, a few droplets always seem to fall? Why doesn't the heavy shower begin at once? While freezing water, for example, some parts of the water such ...
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Reference for Galileo's Law of Motion

It is stated in some places that one of Galileo's laws of motion is that two objects in free fall in a local gravitational field with different densities will hit the ground at the same time in a ...
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3answers
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What would happen if an astronaut tried to swing a baseball bat in free fall?

I am interested in finding out how swinging a baseball bat or similar object would affect the astronaut's rotation in free fall, on the ISS for instance. How much would the astronaut swing the bat, ...
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7answers
472 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 ...
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0answers
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Hydrophobic surfaces and free fall

Does a hydrophobic surface, like Teflon or an "oily" plastic entirely repel water droplets when there is no force (such as gravity) forcing the surfaces together - or is there still some ...
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2answers
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Why do objects not fall faster if you wait?

I am currently reading the book "universe in a nutshell". I reached the point where Einsteins Equivalence principle is explained. It states, that you can't distinguish if your in a space ...
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3answers
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Is an orbiting object traveling along a geodesic in general relativity?

I am getting a layman's understanding of General Relativity. I understand that gravity is understood to be an objects propensity to travel along a straight line in curved spacetime. Would an orbiting ...
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4answers
459 views

If an object is free falling under gravity, then where is the pseudo force applied? [duplicate]

If I am travelling in a train and the train accelerates forward then I experience a pseudo force backward. But if someone is free falling under gravity where does he experience pseudo-force because ...
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5answers
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Falling elevator filled with water

Greetings physics superhumans! If an adult human person is floating in a free-falling elevator, sealed and filled completely with water (no air space), that is damaged on impact in normal elevator ...
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4answers
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What do “tangential and centripetal acceleration” mean for non-circular motion?

We shoot an object of mass $m$ with velocity in the horizontal direction, $u_x$ and with velocity in the vertical direction, $u_y$. The trajectory of the object is the combined result of a free fall ...
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1answer
28 views

Are the particles in the accretion disk in free fall around the black hole?

I know that black hole can feed off the material in the accretion disk and gain mass, the accretion disk is also powered by the black hole to move at a fraction of speed of light. I am wondering are ...
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1answer
25 views

What is ground speed when falling vertically? [closed]

Ground speed as apposed to air speed. Assume a vacuum around the earth for simplicity. Just wondering if it's 0 or the absolute velocity versus the point of impact on the ground?
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4answers
86 views

Why does a body falling down follow this pattern of velocity?

I was wondering about the pattern of velocity for a body falling down with initial velocity $u= 0$ and $g = 10m/s^2$. Without using the formula , I thought : Velocity would change in this manner (...
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1answer
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Question of ball falling down.Difficulty in understanding the formula

A ball is thrown upward from the top of a tower 40m high. u = 10m/s.Find time for it reach AD. g = $10m/s^2$. Taking upwards direction as +ve and downward as -ve. u = +10m/s.$g=-10m/s^2$.s=-40. $-40 = ...
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1answer
49 views

Diffentiating a gravity field to get the radius from a planet center as a function of time [closed]

I'm trying to solve a differential equation to get the radius from a planet as a function of time during a free fall. $$ g=\frac{d^2r}{dt^2}=\frac{GM}{r^2}. $$ Is this statement true? $$ [r^3]d^2=GM(...
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1answer
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Speed, acceleration, accelerating acceleration, etc. How do we know where to stop?

I am not a physicist. Suppose a body A is falling towards body B in a vacuum. We know that A's speed will increase. However, as A draws near to B, the force of gravity will increase so the rate at ...
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Displacement time graph- aerodynamic drag

In the displacement vs time graph of an object in free fall, the parabola with aerodynamic drag is much more steeper on the way downwards of the object than the parabola in which air friction is ...
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Jumping without a parachute — how much horizontal velocity can you achieve?

I am curious about the old chestnut of falling from an extreme height -- perhaps 1,000 meters or more -- and whether it is possible to convert most of the vertical velocity to horizontal, or any ...
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2answers
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Calculations of Earth falling into the Sun if it suddenly stopped orbiting? [duplicate]

If the earth stopped orbiting the sun, it would be pulled by the Sun's gravity and fall into it. How much time it will take is tricky as force is inversely proportional to square of distance. So I ...
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34 views

When do these two point charges meet? [duplicate]

Two point charges in the vacuum (so ignore all frictions). They have opposite signs so they will move towards each other under Coulomb's force. The magnitude of their charges are $q_1$ and $q_2$ ...
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3answers
37 views

Velocity when touching ground and when fully stopping at arena

So my doubt is: my teacher told us that when a ball hits the ground, the velocity isn't 0, but I've encountered a problem that involves a ball falling (free fall) to the sand, and when hitting the ...
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1answer
87 views

Would it be correct to say that the Earth accelerates toward us when we fall?

By relativity theory, would it be correct to say that a planets surface accelerates toward us when we jump and then fall toward it? Or both (a planet and a person) do?.
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1answer
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Does mass has any influence on a horizontal launch?

Really short doubt. Let's say I have 2 objects, with masses 3kg and 4kg, both are thrown horizontally with the same initial velocity, both will touch the ground at the same time right? Because g ...
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Free fall of two point particles in general relativity vs. Newtonian mechanics

In general relativity (GR) the equation of free fall of two point particles which start from rest at some finite distance $r_i$ is strikingly similar to the equation of free fall in Newtonian ...
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1answer
45 views

Pressure and bounce height of a ball

Is there a physics way to explain why higher pressure makes the ball bounce higher? It is allowed to free-fall at a certain fixed height. For different pressures, the ball bounce to different heights. ...
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3answers
58 views

Maximum horizontal distance of a freefalling ball with one allowed bounce anywhere along its initial path?

I was washing a spoon in the sink and this question popped into my mind: If a ball is dropped from height H and is allowed a single deflection of any angle $0 < \theta < 180$ at any height $ 0 \...
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1answer
45 views

How would you go about scientifically comparing the physics of a game and real-life through gravity?

A bit of a hypothetical situation for y'all here. Let's say you want to test a video game's accurateness with regards to its physics; by seeing how closely the game's physics matches up with real-life ...

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