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Newton's Law of Gravitation, Gauss Law and GR

From One of My Unpublished Papers $$\frac{d^2 x^{\alpha}}{d\tau^2}=-\Gamma^{\alpha}_{\beta \gamma}\frac{dx^{\beta}}{d\tau}\frac{dx^{\gamma}}{d\tau} \tag{1}$$ For radial motion in Schwarzschild’s ...
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4answers
4k views

Why do objects fall at the same acceleration?

I read these two posts and now I am more confused. Do heavier objects fall faster? Don't heavier objects actually fall faster because they exert their own gravity? I was going to ask: if mass ...
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3answers
122 views

How can you explain objects of unequal masses falling at the same rate using GR?

Isn't gravity caused by the curvature of space-time, and the stronger it's curved the stronger the attraction? it makes more sense to me that if a heavier object is falling on earth it would fall ...
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3answers
918 views

How does artificial gravity reduction (weightlessness) work on Earth?

Some of us have been to those amusement park/carnival/theme park rides where you enter some capsule/machine, and you will float, etc. There is also some other thing where you go inside a big room ...
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3answers
190 views

Was Aristotle Actually Correct About Gravitation? [duplicate]

Apparently, Aristotle reasoned (without experimentation) that heavier objects must fall to Earth faster than lighter objects. For example, a 1,000 kg ball of iron would fall faster than a 1 kg ball ...
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2answers
600 views

Free fall and projectile motion

I'm wondering if something is falling say from a roof, would the distance it falls be the final $y$ position? Also would all the $y$ components (velocity, displacement) be negative?
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1answer
413 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 ...
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1answer
213 views

Surviving Free Fall with the Help of Mr. Bernoulli

What is the best strategy to survive a free fall naked out of a jetliner at cruising altitude (ignoring temperature)? For instance, my strategy would be to streamline my fall so that my terminal ...
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2answers
45 views

How can I clarify the difference between free falling and Newton's law?

After I have viewed two experiments the first about Newton's law which involves a brick block and feather letting them fall one time in a vacuumed room they fall at the same time and another time in ...
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2answers
379 views

What would happen if you dropped iPhone from Outer Space? [closed]

I read this article where the title suggests the iPhone was dropped from space, but it looks more like it was dropped from an airplane I would think that if astronauts dropped an iPhone from space ...
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2answers
89 views

orbitting around the earth

Does a space station need an initial velocity (tangentially) to be able to orbit around the earth or just the gravitational force acting downward on the station at certain height from the ground is ...
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2answers
12k views

Why do objects with different masses fall at the same rate? [duplicate]

Possible Duplicate: Confused about the role of mass Today we were in our Literature class talking about the Renaissance and the Enlightement and our teacher also said that scientific ...
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2answers
1k 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 ...
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2answers
31 views

Free falling object with air resistance, what's the velocity as a function of time?

So, I'm looking into how velocity can be represented as a function of time when the air resistance is also function of velocity. The force of drag is $$ F_d = C||\vec{v}||\vec{v} $$ where $C$ is an ...
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1answer
57 views

Application of Mean Value Theorem to Law of Universal Gravitation

I'm not terribly well-versed in physics, so forgive me if this is trivial. Supposing an object hovers $6*10^5$ metres above Earth's surface, calculate its impact speed after falling to earth's ...
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1answer
57 views

Will a cyclist be able to pedal during free fall?

Assume that he is seated on the cycle and his waist is tied to the seat.
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1answer
138 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 ...
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1answer
43 views

Maximal Velocity of an Object in Free Fall

A baseball is dropped from a high point. Since the velocity is large, we can say that the drag force is proportional to the square of the velocity, $F_d = \gamma v^2$. My goal is to determine the ...
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2answers
128 views

Tidal forces in free fall

Would a body free falling in a gravitational field which has a gradient large enough that it would affect the free falling body 'feel' the effect of the tidal forces on it. I'm curious because would ...
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2answers
169 views

Simulate free fall in a rotating torus?

Say I have a rotating torus filled with air at 1 atmospheric pressure at sufficient speed (and inclined along the direction of the force of gravity with respect to Earth). If the rotation speed were ...
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1answer
700 views

Will a free-falling rod (without drag) rotate?

When we consider a bicycle is turning on a flat plane, we know that there is friction, which provide centripetal force on the bicycle. And we know that the bicycle is no longer perpendicular to the ...
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1answer
952 views

Energy used to stop / slow an object

I'm trying to workout how much energy (if any), I use (imagining me as an efficient machine rather than a complex bio-mechanical human) when I lower or catch a weight. I understand that when I push it ...
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3answers
75 views

Reach @ jumping from one building to another

Let's assume I'm in the rooftop of a building (Building A) and want to jump to the rooftop of another building (Building B). Forget about injuries... is just hypothetical. Building A has a height of ...
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1answer
37 views

Solve the inverse function of the solution to a varying acceleration problem ODE

Suppose there are two positive charges $A$ and $B$, both with equal mass $m$ and the same charge quantity $q$. The initial distance between $AB$ is $R$; and the initial velocity of $B$ relatively to ...
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1answer
79 views

Mimicking Free Fall

I was thinking about this situation with a friend of mine, and we had opposing views: Suppose you have a frictionless table with mass M resting on top. You attach a chain to the mass M, a chain with ...
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2answers
81 views

Derivation of a kinematical equation [duplicate]

My question is, we can calculate distance of free falling objects with the equation of $d = \frac{1}{2}gt^2$ where $d$ is distance in meter, $t$ is time in seconds, but I wonder how we achieved this ...
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1answer
49 views

Physics Problem: Falling Rocket [closed]

A rocket, of mass $M = 40kg$, falls vertically with a speed of $60 m/s = v_0$ and explodes in two fragments of the same mass when it's at $H=2km$ from the ground. Immediately after the explosion one ...
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1answer
109 views

Probability Density of a freely falling body

The following question has been taken from David J Griffith's Intro to QM. This is not my homework! :D Suppose I drop a rock off a cliff of height $h$. As it falls, I snap a million photographs, at ...
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4answers
508 views

Why is displacement negative during free fall?

I am confused by this question. Displacement is shortest path travelled by an object, but I had seen in my book that during free fall displacement is negative.
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1answer
69 views

How can I solve this differential eqution with IVP? [duplicate]

$$m\frac{d^2r}{dt^2}=-G\frac{Mm}{r^2}, \qquad r(0)=R ,\qquad \dot{r}=v_0>0$$ describes the free fall of an object of mass $m$. $r(t)$ is the distance of m to the center of the earth which is $R$ ...
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4answers
356 views

Car driving / falling off of a cliff - will it land upright?

In a recent episode of The Walking Dead, a van was pushed off of a bridge and flipped once and landed upright, on all four wheels. Assumption: the ground and cliff are both flat. Will a vehicle ...
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2answers
89 views

Is it really okay to treat the Earth as stationary when doing free fall experiments?

Typical treatments of free-fall experiments treat the the Earth as fixed. Using this model, object being dropped moves toward Earth, but the Earth doesn't move toward the object. A more detailed ...
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1answer
1k views

free falling object with air resistance?

we already know that if we plot speed vs time of free falling object it will be y=gx graph because we know the acceleration is gravity. If it have air-resistance acceleration will be change right?. ...
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1answer
424 views

Container of liquid in free fall

Imagine a container of liquid in free fall. Why does the liquid fly out of the container. Is there a force exerted by the inside fluid on the surface of liquid which causes this? Also, suppose there ...
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1answer
224 views

Question about weightlessness

Let us consider +Y as upward and -Y axis as downward. So the acceleration that works these objects is always $-g$. For the first picture, if the lift is going upward with acceleration $a$, then ...
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1answer
390 views

Calculating the launch angle of a horizontal launch (mechanics) [closed]

I need some help with the following question: A smooth spherical object (the first object) is projected horizontally from a point of vertical height H = 26.38 metres above horizontal ground with a ...
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1answer
40 views

Why will you float in free fall with 0 relative acceleration?

Imagine you are in an elevator that is falling freely to the surface of the earth. You begin to float. However you and the elevator have equal acceleration. Why is it that you begin to float with ...
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1answer
21 views

Equation for Turning Projectile

I'm trying to cook up an equation that will give me position for a projectile which operates in the Newtonian Domain. So a the fall equation is: $$\mathbf{p_t} = \frac{\mathbf gt^2}{2} + ...
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1answer
45 views

What's the average speed (along $z$) and the average position (along $z$) of an object in free fall?

I'm looking to calculate the average speed (along z) and the average position (along z) of an object in free fall. The initial instant is $t_0$ and we have: $z(t=t_0)=z_0$ $v_z(t=t_0)=v_0=0$ I ...
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0answers
37 views

Galileo proved wrong? [duplicate]

Galileo stated that objects dropped from the same height will hit the ground at the same time, that the rate of gravity is constant for all objects no matter the mass. But I think there is a flaw in ...
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2answers
115 views

Does center of mass affect how an object falls?

Suppose you drop an object which has tow ends, of which one is heavy and the other is pretty light. Will the object fall with its heavier end downward or with the lighter one? Why does it happen?
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1answer
117 views

Free-fall path into a black hole in Kruskal Coordinates

If an object at t=0 begins to free-fall into a black hole from X in Kruskal coordinates (https://en.wikipedia.org/wiki/Kruskal%E2%80%93Szekeres_coordinates), what does its path on the Kruskal-Szekeres ...
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0answers
126 views

Impact force on a Full Suspension Mountain Bike

I have a full suspension MTB design and i will do a structural analysis using a FEA tool.For this purpose,i have to calculate the forces applied on both wheels when the bike falls from a certain ...
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3answers
172 views

What physics concepts support the observation of the book and paper falling together?

you place a sheet of paper on a book, it falls with it rather than being separated & slowed by air resistance. What physics concepts support the observation of the book and paper falling together? ...
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0answers
107 views

What is the relationship between the Young's modulus of a material and the elasticity of a free fall collision

I'm coding a 2D physics simulator based around the Newtonian physics principles with some alterations due to computation limits and I am at the stage of creating a collision event between a planetary ...
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0answers
16 views

A falling object's position [duplicate]

I have asked this previously, with a very useful answer but I was not able to solve my problem. I'll try to make it more simple, basically: Find the radius, $r$ of an object after a time, $t$ if ...
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1answer
213 views

What is the final velocity of a stone dropped out of a rising balloon? [closed]

A balloon is starting from the ground has been ascending vertically at uniform velocity for 4 sec and a stone let to fall from it reaches the ground in 6 sec. Find the velocity with which the stone ...
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0answers
21 views

Two Dimensional Kinematics and Projectile motion [duplicate]

I have a question. So a baseball is hit with a velocity of 30 m/s at 42.6 degrees to the ground. A fielder who is supposed to catch the ball is smart and knows that he is exactly 8 meters from where ...
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0answers
43 views

Radius of a falling object [duplicate]

I have asked this previously, with a very useful answer but I was not able to solve my problem. I'll try to make it more simple, basically: Find the radius, r of an object after a time, t if the ...
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0answers
135 views

Relationship between the fall time and projected area

I am investigating the relationship between the fall time of a paper tray and its projected area. In this investigation I have been using the following variables: Controlled Variable: The air ...