The Newtonian model of gravity in which the force between two objects is given by GMm/r^2.

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12k views

If mass is added to a toy car does it affect its speed making it faster

If mass is added to a toy car (29.7g) and dropped down a wooden ramp would it affect its speed making it go faster? I know friction comes in to play to, so if you could give me an answer or an ...
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0answers
16 views

Gravitation Field Lines (amount) and Size of a body

Let's say there were two planets, planet A, and planet B. If they both had the same mass, but one was twice as massive as the other planet, how would the field lines of the two planets differ? I know ...
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2answers
106 views

Calculate the Earth’s velocity in its orbit (assumed to be circular) around the Sun [closed]

Data: GM of the Sun: $\text{GM} = 1.327 \times 10^{20} \;\mathrm{m^3 s^{-2}}$ Radius of the Earth’s orbit: $r_{Earth} = 1.496 \times 10^{11} \;\mathrm{m}$ Orbital period of a planet in seconds: $T = ...
6
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2answers
776 views

How general relativity gets to an inverse-square law

I understand that a general interpretation of the $1/r^2$ interactions is that virtual particles are exchanged, and to conserve their flux through spheres of different radii, one must assume the ...
3
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2answers
63 views

Liquid seperation in space

We know if we take immiscible liquids of different densities then they form different layers on earth. But when we take them to outer space, they form tiny droplets which are energetically most ...
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5answers
1k views

Zero gravity means zero friction?

The frictional force acting on a body placed on a horizontal plane is $F=\mu{R}$ where $R$ is the normal reaction and is equal to weight of a body in this case. And $\mu$ is the coefficient of ...
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2answers
57 views

Gravitational potential and intensity

Why don't we calculate gravitational field/intensity of a point due to a disc directly? We first calculate the potential then calculate the field by differentiating with respect to $dr$. Why don't we ...
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2answers
46 views

Exertion of force due to spin of Earth

If Earth were to spin at a different speed would I be experiencing a different weight?
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4answers
143 views

Is cause of this equilibrium - tension or friction?

This is a very odd problem which I have. As you can see in the diagram, the string is taut. So, if there was no friction you could clearly say that tension is balancing it or if there was no tension ...
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0answers
38 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
79 views

Could one extra straw literally break a camel's back? [closed]

I thought this was better suited here than biology, as the camel is figurative; it could also be a wooden beam. My question is basically: Could adding an object of negligible weight (such as a straw) ...
0
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0answers
33 views

Explanation for Spiral galaxies [duplicate]

Can anyone explain to me why our galaxy is spiral and not irregular or spherical? Please be specific and if maths is required to state what you mean precisely, use it. I will understand it much better ...
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0answers
26 views

Collisions with the earth [duplicate]

The earth is traveling around the sun at around 65,000 mph. An asteroid or other large object is traveling around 35,000 mph. Depending on the direction of the impact, the object could strike head on ...
2
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1answer
52 views

Given an equation of an elliptical orbit, is it possible to find satellite´s speed at a certain point?

As the heading says: given an equation of an elliptical orbit, is it possible to find satellite´s speed at a certain point? I'm playing a bit with simulations of planets and satellites in the solar ...
3
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1answer
151 views

Inaccuracy at measuring gravity constant with Cavendish experiment

For a scientific work for school I decided to measure the gravity constant with the Cavendish experiment. I set up a structure like the one suggested on this website: ...
1
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1answer
53 views

Gravitational PE lost v Elastic PE gained in mass - spring

If a spring has a load $m$ added to it (and so is extended by $x$), the gravitational potential energy lost by the mass will be $mgx$. The elastic potential energy gained by the spring is ...
3
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2answers
76 views

Multiple Definition For Gravitational Potential Energy?

This may just be a simple Misconception Question, here goes: Definition for Gravitational Potential Energy: The work done by gravity to pull an object to the ground. ...
12
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4answers
1k views

Two planets in same orbit - not planets?

Let us pretend for a moment that there are two identical planets that are exactly opposite their star from each other and are the same distance from said star. (This would make them, at all times, ...
2
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0answers
24 views

Initial conditions for a massive objects to follow a path

Suppose I have a path, such as the one traced out by $r^2 = \cos(2\theta)$, and $n$ objects with mass $m$ at equidistant points on this path. What velocities should each object initially have in order ...
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1answer
101 views

A question on Rolly polly dolls

I was reading on rolly-polly dolls when the following questions crept into my mind How exactly does center of gravity play a role which helps rolly-polly doll to stand up on its own? Can a ...
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3answers
248 views

Deceleration of a bullet [closed]

Taking into account gravity, air resistance, and wind velocity and direction. (And also temperature if it's actually relevant.) I know the muzzle velocity, the total distance the bullet traveled, its ...
0
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1answer
36 views

In a Dyson shell, could centripetal force act as gravity?

In a pure Dyson shell surrounding a non-moving star, with the shell rotating around the star, could the centripetal force of the shell act in some way similar to gravity toward the interior of the ...
2
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1answer
98 views

What is the net effect of gravity of a thin ring on a point on itself?

Consider a thin ring of mass $M$. What is the net force on any point on the ring caused by the gravity of the other points on the ring? My intuition for this problem was to find the linear mass ...
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4answers
8k views

What causes a soccer ball to follow a curved path?

Soccer players kick the ball in a linear kick, though you find it to turn sideways, not even in one direction. Just mid air it changes that curve's direction. Any physical explanation? Maybe this ...
3
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4answers
14k views

What is the general formula for a trebuchet?

What I'm really looking for is a formula for a trebuchet that I can input the desired initial velocity after launch and mass of the object, and from that figure out how long the long arm, short arm, ...
0
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2answers
61 views

Can two artificial bodies be built in space and be made to orbit each other?

Would it be possible to make artificial constructs (satellites) orbit each other? I looked at the gravitational laws, and nothing seems to suggest that this is not possible.
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2answers
492 views

Rivers that flow “uphill” due to Earth's rotation

One of the fun tidbits that gets bandied around in physics departments is that the Mississippi River actually flows away from the center of the Earth. Due to the Earth's oblateness, the source of the ...
2
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1answer
77 views

Will the Earth's rotation someday be synchronized with its revolution around the Sun?

When will the earth act like the moon with regard to one side of the moon always facing the earth. Will the earth one day get locked in a rotational orbit that has one side of the planet facing the ...
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1answer
193 views

How to calculate escape velocity and orbital velocity for a cubular planet?

Given a planet that is a cube, how would one calculate the escape velocity and the orbital velocity? For a circular planet with an even distribution of mass (aka center of mass=center of volume) the ...
42
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8answers
8k views

Are we slightly lighter during the day and slightly heavier at night, owing to the force of the Sun's gravity?

Using $g = \frac{Gm}{r^2}$, the force on a point mass located at 1 AU from the Sun ($m = 2 \cdot 10^{30} \text{ kg}$) is about ~0.006 N/kg. Does that mean that, e.g., a 70 kg person is ~42g lighter ...
3
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1answer
194 views

Can we regard dark matter as a special fluid rather than individual particles?

If we assume that dark matter is an $N$-body system of sizeless and collisionless particles which only interact via newtonian gravity, do these huge quantity of particles manifest some collective ...
1
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1answer
341 views

How does the Moon cause the tides?

I am considering the following question, but I can't quite figure it out... I have looked up differential gravity, but I cannot derive the equation for the effect on Earth, and I haven't found any ...
8
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7answers
872 views

Distribution of Gravitational Force on a *non-rotating* oblate spheroid

Suppose a person is standing on a non-rotating$^1$ oblate spheroid of uniform density. He first stands on one of the poles, then on the equator. In which case is the gravitational force greater? In ...
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0answers
55 views

Why is gravity high at poles but lower inside the surface of Earth, as compared to $g$ on surface? [duplicate]

My high-school physics teacher recently displayed some formulae stating at when we dig deeper the gravity pull is lower but at poles (the flattened part) it is appreciably higher. Now, if we consider ...
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1answer
92 views

What is the outward force on the Moon that makes it go in orbit rather that falling straight to the Earth? [duplicate]

So, we know that the gravity is responsible for pulling the Moon towards the Earth. But because it moves in an orbit, it makes me think that there must be a force that is causing the moon to travel in ...
1
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2answers
980 views

What is the most efficient machine for translating gravitational potential energy of one mass into kinetic energy of a different mass?

As the question states, what is our current best machine for translating falling gravitational potential energy, such as a large weight, into launching a smaller projectile vertically? A lever? A ...
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1answer
455 views

Two objects at different heights, would they be traveling the same speed?

If I were to drop an object at a height of 15 feet, then another object of the same mass at 20 feet, would both objects be traveling at the same speed? What would be the speed of which they are ...
0
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3answers
76 views

Finding velocity from distance and gravity

Basically, I have a problem that asks: An object is launched to a height of 2 miles, what was it's initial speed and time. Now normally something like this would be fairly basic. The problem ...
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4answers
1k views

Is it correct to say that falling object are standing still?

As I was browsing youtube I came across the BBC video "Brian Cox visits the world's biggest vacuum chamber - Human Universe: Episode 4 Preview - BBC Two" He drops a bowling ball and a feather in a ...
2
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1answer
177 views

Newton's shell theorem in 2d [closed]

I was wondering how to prove the analog of Newton's shell theorem for 2 dimensions, in which gravity obeys an inverse-linear law. Meaning: that an anywhere inside a circle, the gravitational field ...
0
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2answers
75 views

Do other people's mass count when measuring the attraction of the earth on me? [duplicate]

Suppose that I'm alone on a planet of $M$. From what I learned from school, the gravitation force acting on me is given by $$F=G\frac{mM}{r^2},$$ where $m$ is my mass, $r$ is the distance between me ...
2
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2answers
53 views

Does $v^2=v_0^2-2gh$ work if the positive axis is up and the initial velocity is down?

In the situation where the positive axis is up, the acceleration due to gravity is $g$, and the velocity is represented by the equation $v^2=v_0^2 - 2gh$. This works great if the initial velocity is ...
0
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1answer
64 views

Why aren't Roche limit and the difference in gravitational acceleration the same?

The definition of the Roche limit is: "The distance within which a celestial body, held together only by its own gravity, will disintegrate due to a second celestial body's tidal forces exceeding the ...
2
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5answers
632 views

Why Newton's law of universal gravitation is a valid law? What causes any two bodies in the universe attract each other with a force?

Why Newton's law of universal gravitation is a valid law? What causes any two bodies in the universe attract each other with a force? What causes a larger body in space to have a gravitational pull on ...
18
votes
5answers
14k views

A force opposing Gravity

Every Action Has An Equal and Opposite Reaction (Newton's Third Law.) If this is the case, does gravity have an equal-opposing force? From asking around I still haven't got a very clear answer; ...
0
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1answer
81 views

What mistake am I making in plotting this graph of effective potential for the Earth-Moon system?

I am trying to create a graph of effective potential for the Earth-Moon system in Excel. It should result in a graph that looks like this: But this is not what I end up with. (I've made a Google ...
12
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2answers
3k views

Slinky base does not immediately fall due to gravity

Why does the base of this slinky not fall immediately to gravity? My guess is tension in the springs is a force > mass*gravity but even then it is dumbfounding.
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4answers
111 views

Does not the mass of those living on the Earth add on to the mass of the Earth or is it too negligible to be cared for?

Source: Earth weighs about 13,170,000,000,000,000,000,000,000 pounds (or 5,974,000,000,000,000,000,000,000 kilograms). Since Earth is too big to be placed on a scale, scientists use mathematics ...
2
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2answers
155 views

Gravitational Null Point between Earth and Moon

I need help finding the gravitational null point point between the Earth and the Moon, the point beyond which you start falling towards Moon. I am having difficulty in taking into account the orbiting ...