Gravitational potential Definition and 389 Threads

I thought I know introductory physics well but now I'm confused about simple things! Imagine a pendulum. Its released from rest from a height. We take that height to be the zero level of the gravitational potential. But that means its total energy is zero at the beginning and because of the...

Homework Statement An asteroid of mass m = 2.6 × 10^6 kg approaches the Earth. When it is exactly 3 Earth radii away from the Earth's centre its speed relative to the Earth's centre is u = 8.7 × 10^3 m s–1. The asteroid subsequently falls down to the Earth's surface. You may assume that the...

Homework Statement To explain the forces at work when a marble is released from a height and then eventually comes to rest. We did this experiment where two lengths of hose pipe were taped together. The hosepipe was then bent into a semicircular shape (forming a track) and secured onto a clamp...

Hello my name is Aaron! I am a high school senior from northeastern Kentucky designing a pneumatic system of sorts for a science competition and need some help. I will be building a device that converts gravitational potential energy, from a falling mass, into air pressure (or possibly the...

I understand the derivation of gravitational potential energy when an object is moved away from Earth but when I try to derive the formula for gpe by considering a test mass moving from infinity to r then I end up with a positive gravitational potential energy. Because integrating F.dr from...

is GPE at a point the work we must do against the gravitational force to bring an object from infinity to the point? Or is it the work done by the gravitational force?

This question may sound weird but when we lift an object with a force equal to the weight of the object up to a certain height the Earth is doing negative work on the object as well. So shouldn't the net work be zero?

Homework Statement Here is the pic: http://i.imgur.com/olnuDjL.jpgHomework Equations The Attempt at a Solution So intensity was pretty easy, it came up to be y=\frac{GM}{a^{2}}(1+\frac{1}{2\sqrt{2}},1+\frac{1}{2\sqrt{2}}) Check on if it's correct would be nice aswell. Now for potential I know...

Homework Statement So in this video: https://www.youtube.com/watch?v=rm3x2X0X_Sc&t=210 Why does g.out and g.in have values as shown on the video? I can not for life of my understand it. Homework Equations The Attempt at a Solution

Homework Statement I'll provide a picture for a clearer view: http://i.imgur.com/wkXPcJn.jpg Suppose that the slender rod starts at rest at theta = 0. For convenience we chose the datum at theta = 0. Now I want to calculate the gravitational potential energy at a later instant when theta =...

Gravitational Potential energy is the work done against the gravity to move a mass from one point to the other. So if a mass was falling down to the earth, how is the potential energy defined?

Why is gravitational potential energy defined at infinity? Like here on Earth there is Zero potential energy at the center of the Earth (if you could theoroeetically go there) so why not define it as 0 at zero distance from the force supplier instead of at infinity? I understand why the...

There is several things I am confused about with gravitational potential energy. So, first of all, shouldn't U=mgh always be written ΔU=mgΔh, because isn't that equation only dealing with differences of potential energies when close to the surface of earth? Second, with the equation U=-GMm/r...

http://www.aapt.org/Programs/contest...08_fnet_ma.pdf Homework Statement A uniform circular ring of radius R is fixed in place. A particle is placed on the axis of the ring at a distance much greater than R and allowed to fall towards the ring under the influence of the ring’s gravity. The...

Hi - I have a question about wormholes, specifically when the two endpoints have a differnt gravitational potential. If we imagine the technology extisted to create a person sized wormhole between say the Earth and the moon, I think the popular perception would be that one could simply walk...

I don't get the difference between these equations: U = \dfrac{-Gm_1m_2}{r} F_g = \dfrac{-Gm_1m_2}{r^2} g = \dfrac{F_g}{m} = \dfrac{GM}{r^2} Also, why are the first two negative? Here's my thinking: The first equation is like U=mgh. Except it's when two masses are very far apart. It...

Hello , I was thinking about dams and hydroelectrostations , the turbines can turn because the water before the dam is higher than after it so there is stored potential energy waiting bto be released, Now I wonder if we were to take two places one at the water surface level in the dam reservoir...

Homework Statement What is the gravitational potential energy of a system of 8 masses of 10 kg each placed at the corners of a cube of length 0.25 meter apart. Homework Equations U=-G*m1*m2/r The Attempt at a Solution I have actually taken one particle pair at a time and sum all...

Homework Statement Consider the Earth's radius to be 6.40x103km, its mass to be 6.00x1024kg, the Moon's mass to be 7.36x1022kg, and the Moon's radius to be 1.74x103km. The average value for the Earth-Moon distance is 3.84x105kg. Neglect friction and rotation. a. Sketch the potential...

Hi, I've managed to get myself confused over the simplest thing. Intuitively I'd think that gravitational potential energy is proportional to distance as described by the near-body equation GPE=-mgh. The alternative for farther bodies (-G*M*m/R) has me confused because it is inversely...

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I'm trying to find the avarage enerrgy of an ideal gas when it's under a gravitational potential. I know how to obtain the kinectic avarage energy but the potential energy depends upon the position of each molecule. There is a avarage height lo look for in order to determine this potential term?

I am wondering how this all works and am hoping to get some guidance. If a 1000 lb weight freefalls vertically from 660 ft the energy is 894,289 joules. If the fall is down a 30 degree slope that is 1300 ft long, then it takes 17 seconds and the potential energy can be said to be 53 KW. If...

I got an exam tomorrow and while i was studying, this popped in. Is there a gravitational potential inside a mass (eg : 500 km deep from the Earth surface)? We can calculate the Gravitational field intensity inside a mass by taking the distance from the center to that inner-point as x and...

Gravitational potential is always a negative value according to the theory. As per to the equation V = - \frac{GM}{r}; when the r (distance) increases the potential decreases. But considering the potential at infinity as zero and since this a negative value, on what basis do we consider the...

Hello! I'm having some problems with a question that my professor has given me. Below is the question. I have already figured out the planet's orbital and angular-orbital velocities, but included that part due to the fact that some information was included. PICA-9 and PIC-10 are planets...

This isn't a homework problem, but something that has being buzzing in my head. I've been thinking about it cause at huge distances from Earth g changes and also in what happens for really dense objected and small things could change too. The real equation for gravity no matter which body...

Homework Statement gravitational potential at surface of the Earth = -63MJkg-1 gravitational potential at surface of the moon = -2MJkg-1The attempt at a solution I thought gravitational potential was a scalar, so in which case, you would surely just add up the potential due from both masses...

Hello, I'm a high school student studying for the AP Physics test tomorrow. I've been having trouble proving the negative value of gravitational potential energy through working out the work integral. I will greatly appreciate any help and clarification. Homework Statement Find the change...

Homework Statement A rocket is launched straight up from the Earth's surface at a speed of 1.80×104m/s . What is its speed when it is very far away from the earth? Answer in m/s Homework Equations K1+U1=K2+U2 The Attempt at a Solution .5mV1^2-(G*m*Me)/r= .5mV2^2-(G*m*Me)/r *** THe mass of...

The medium gravitational potential must have been higher in the past than today (assuming constant mass/energy and an expanding universe). That said it would mean that the effective speed of light in any place of the past would have been slower than today (assuming a constant c at constant...

Homework Statement A meteorite impacts a flat-tabular Earth (with a density of 6gm/cm^3). During transit, the meteorite is observed to have a density of 8 gm/cm^3 and to be a perfect sphere of radius 1km. The meteorite penetrates the flat Earth to an unknown depth to center mass, z_0; z_0...

Homework Statement Find the total gravitational potential energy stored in a sphere with a 1/r2 density distribution if the total mass is 6.7 solar mass and the radius is 1.3 solar radius. Express you answer in units of 1041 Joules. The Attempt at a Solution To derive the equation, i...

http://www.scholarpedia.org/article/Celestial_mechanics#Newton.E2.80.99s_Celestial_Mechanics In this source, the gravitational potential energy is given as \frac{-MmG}{r}-\frac{mmG}{r}, seeming to imply that the \frac{MmG}{r} result only applies to a body, mass m, in a gravitational potential...

Homework Statement A 3.0 kg object travels vertically at a constant speed of 2.0m/s. What is the increase in gravitational potential energy after 4.0 sec? Homework Equations Ep=Mgh The Attempt at a Solution I know i need to find the height but, with constant velocity i don't know...

Hi, The derivation of the Gravitational Potential formula, as I understand, is: W = Fd (1) W = G \frac{M_1m_2}{r^2}d (2) Substituting the Gravitational Force formula W = - \int_R^∞G \frac{M_1m_2}{r^2} \, dr (3) Integrating within the boundaries of the initial distance (R) and...

Homework Statement A simple pendulum is swinging. Its mass is m and its length is L. What is its gravitational potential energy if it is oriented at 30° with respect to the vertical? (Let gravitational potential energy be zero if it is in the vertical orientation). Homework Equations U =...

Homework Statement A watermelon with a mass of 2.0kg falls out of a tree house that is 5.4m above the ground. What is the speed of the watermelon just before it hits the ground? Homework Equations Δh = (vi^2 - vf^2)/2g Eg = mgΔh Ek = 1/2mv^2 The Attempt at a Solution I tried two...

Homework Statement Explain why the kinetic energy of the skier at the bottom of the hill is not equal to the gravitational potential energy of the skier at the top of the hill. Homework Equations n/a The Attempt at a Solution I think the answer is because the bottom of the hill is...

Homework Statement Four masses m are arranged at the vertices of a tetrahedron of side length a. What is the gravitational potential energy of this arrangement? (answer is -6Gmm/a) Homework Equations gravitational potential energy = -Gmm/r The Attempt at a Solution One mass is "a"...

Hi, my question regards the average (cosmic) gravitational potential and its variation over space. I have not been successful finding a good reference on this subject, other than phi=-c^2. The background gravitational potential on Earth is not necessarily equal to the average cosmic potential...

Homework Statement Homework Equations I need help solving intergral… \int \frac{dx}{(a+x)^2} The Attempt at a Solution I found the integral for… \int \frac{dx}{(a^2+x^2)} = 1/a arctan x/a But I don’t know how to apply that to the original integral which is a little different...

So I am given that the gravitational potential of a mass m a distance r away from the center of a spherical shell with mass m' is -Cm'/r for m outside the shell and constant for m inside ths shell. I am to find the potentials inside and outside a solid sphere (the earth) of radius R as well...

How did scientists derive the formula -GMm/r=Ep in order to calculate the amount of work required to move an object from an infinitely large point (or an extremely large distance as my textbook says) ?

So, the gravitational potential energy of a mass "X" from the sun is, let's say, 100joules. Why is it that when we take the gravitational potential energy of the mass from the reference point of infinity that the gravitational potential energy is -100joules? I understand the negative...

Hi! So, when we're calculating the potential energy of a mass in space we make it negative because we assign infinity as the reference point. Now, to find the potential energy of something I understand that we find the work that is done to it to move it from the reference point to another...

Homework Statement I am asked to calculate the gravitational potential of the ring at the point Q. I can do this for point P, but Q is killin me... Homework Equations V = GM/r M = ρ2∏a dM = ρadθ radius of ring = a The Attempt at a Solution Well for the case at point P, it...

Homework Statement a satellite having a mass of 1800 kg orbits the Earth at a distance of 6.3 x 10^5 m above the surface find the gravitational potential energy of the satellite while in orbit, the orbital speed and the binding satellite. The Attempt at a Solution gravitational potential...

Hey guys, I'm having some trouble with the energy topic. So the question is: "Calculate the gravitational potential of Earth and of Mars. Then use that information to calculate the gravitational potential energy required to life yourself completely off each planet" So I got the...

Homework Statement A satellite of mass 750kg is changed from an orbital radius of 7000000m to a geostationary orbit of 4.2*10^4. Calculate the change in its gravitational potential energy Mass= 750 Earths radius= 6380000m Gravitational constant= 6.67*10^-11 Earths mass=6*10^24...