# Tagged Questions

1answer
32 views

### Falling through the ground [duplicate]

I do not know much about physics but I know that according to Newtons third law of motion when we walk we are pushing the ground down but the ground is pushing us up. What force is making the ground ...
3answers
265 views

### Force inversely proportional to the squared distance

Newton's law of universal gravitation: "Newton's law of universal gravitation states that every point mass in the universe attracts every other point mass with a force that is directly proportional to ...
1answer
113 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.
1answer
153 views

### If 2 charges have the same sign, the coulomb force is positive but repulsive, while with 2 masses the gravitational force is positive but attractive

If you have two point objects both the same positive charge and both of the same mass at a distance $r$ from each other. The force between them due to gravity is $F_g=\frac{Gmm}{r^2}$ and $F_g$ is ...
1answer
88 views

### Forces: Worth worrying anything?

I am a general physics student, I had a question in my text-book and according to it two students having gravitational attraction between them = ($6.67\cdot10^-8\ \mathrm{Nm}^2/\mathrm{kg}^2$) is not ...
1answer
205 views

### Gravity force strength in 1D, 2D, 3D and higher spatial dimensions

Let's say that we want to measure the gravity force in 1D, 2D, 3D and higher spatial dimensions. Will we get the same force strength in the first 3 dimensions and then it will go up? How about if ...
2answers
150 views

### Is it possible to use a balloon to float so high in the atmosphere that you can be gravitationally pulled towards a satellite?

A recent joke on the comedy panel show 8 out of 10 cats prompted this question. I'm pretty sure the answer's no, but hopefully someone can surprise me. If you put a person in a balloon, such that ...
3answers
176 views

### Weightlessness by a parabolic flight

Do you actually achieve weightlessness during a parabolic flight? Because I believe I heard somewhere did you achieve 'near-weightlessness' and not 'weightlessness' (if this is true, why is this?) ...
3answers
230 views

### Differences between the gravitational constants $G$ and $g$?

There's a formula (described by Sir Isaac Newton) that gives the force acting between two objects: $$F = \frac{Gm_1m_2}{r^2}$$ And then there's a formula for weight of an object $$w = mg$$ My ...
0answers
21 views

### Helpful tutorials on force [duplicate]

Possible Duplicate: List of good classical physics books I'm having a hard time understanding force in my highschool AP physics class, i looked through youtube but without luck. Could ...
7answers
3k views

### Does juggling balls reduce the total weight of the juggler and balls?

A friend offered me a brain teaser to which the solution involves a $195$ pound man juggling two $3$-pound balls to traverse a bridge having a maximum capacity of only $200$ pounds. He explained that ...
1answer
156 views

### Would the Moon drift away from the Earth due to extraction of tidal energy? [duplicate]

Possible Duplicate: Why does the moon drift away from earth? It seems to me that, due to conservation of energy, the moon would drift away from the Earth if humans began extracting large ...
2answers
177 views

### Hanging a Hammock

I have a hammock that I want to hang using a tree on one end and a wooden post set in a bucket of cement on the other end. How would I determine how heavy the cement needs to be so that it would ...
4answers
537 views

### Questions from elevator ride

I like to play inside the lift (elevator). For instance, there are bars attached at the side of the lift, and I like to hold my body up using my two hands on the bar. I realised that I actually feel ...
1answer
490 views

### Combining Proportions to get Newton's Law of Universal Gravitation

I've read a little on the history of Newton's Law of Gravitation and noticed that the formula can be separated into 3 distinct parts that lead to the end result of $F_g = G \frac{m_1 m_2}{r^2}$; the ...
1answer
145 views

### How do I factor in multiple forces into these Newtonian mechanics equations?

Say a person is walking along. He then jumps. The person weighs $25$kg (irrelevant?). Just after jumping, his velocity is 5m/s (positive is taken as up). Gravity is taken as ...
2answers
212 views

### The two-body problem: What is force between them?

Two bodies with similar/different mass orbiting around a common barycenter. What is force between them, where $F_{12}$ is the force on mass 1 due to its interactions with mass 2 and $F_{21}$ is the ...
4answers
417 views

### what is the 2D gravity potential?

In 3D, I can calculate the total force due to gravity acting on a point on the surface of the unit sphere of constant density, where I choose units so that all physical constants (as well as the ...
1answer
145 views

### Does a slinky hanging downward double in length if gravity doubles?

Also would a spring under tension greater than the force of gravity pulling the spring downward shrink in both directions until it has depleted it's stored energy while in free fall?
2answers
271 views

### When we throw an object in the presence of gravitational attraction is the mass of the object proportional to the time of fall or not?

I was confused when i saw two object of different masses (A and B)falling from the same height(h) but both of them strikes the ground at same time. Is this possible, that masses of the objects are ...
1answer
74 views

### How should I be thinking about tides?

I am working on a project for physics that involves tides. This is my current mind set when thinking about tides: The earth applies a gravitational force on some mass ...
2answers
139 views

### Gravitational attraction [closed]

The mutual force with gravitational attraction between two masses is 500N. a. If the masses are moved 5 times as far apart, what is the new mutual force of gravitational attraction? b. If the masses ...
5answers
2k views

### If the earth has gravity, why don't we all collapse to the center?

I'm sorry if the answer is obvious for you guys, but why don't we all (including buildings, road, people, the ground) collapse to the center of the earth because of gravity? Is it because we have ...
4answers
2k views

### The Time That 2 Masses Will Collide Due To Newtonian Gravity

My friend and I have been wracking our heads with this one for the past 3 hours... We have 2 point masses, $m$ and $M$ in a perfect world separated by radius r. Starting from rest, they both begin to ...
1answer
1k views

### Work done by gravitational field

To calculate the work done by a gravitational field, the equation is written as $$W=GMm(r_\text{initial}^{-2} - r_\text{final}^{-2})$$ Suppose a small mass has distance $R$ from a big mass. So here ...
1answer
6k views

### What is the extent of Earth's gravitational pull?

Where the gravitational pull of Earth exist up to? What distance from Earth it will be zero? How do the skydivers fly at a same altitude? Won't they feel gravitational pull? What is the Earth's ...
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