Gravitational potential energy Definition and 292 Threads

Hi Guys,When we are finding the wasted energy when something is dropped a tower, we do this: mgH-0.5mv^2 My question is, does the velocity of the kinetic energy have to be vertical component, or can it be the impact velocity when it hits the ground? Thanks

Hello, I do not quite get this. Can anyone provide examples? " We may feel that it takes a force greater than the weight of the object being raised to lift it upwards, but it is not so. Provided the force is equal to the weight, the object will move upwards at a steady speed. "

During gravitational collapse, gravitational potential energy of the gas is converted to its internal kinetic energy so the internal energy of the clous of gas is said to be increased But isn't gravitational potential energy included in the internal energy? Shouldn't the internal energy remains...

Homework Statement Consider the equations for electric potential energy: and gravitational potential energy: GPE=m*g*h In the case of GPE, the potential energy increases as the distance between the two objects increases. This makes sense (to me), as the greater distance between the Earth...

Suppose the mass of planet is" M" and there is body in its surface whose mass is "m" and the field strength is "g" . If the body is thrown 1800 m then Gravitational Potential energy = mg(1800). My question is why can't we use formula GPE= GMm/x ? This is also the formula for gpe but why...

Homework Statement Homework Equations ΔPE = G × M₁ × M₂ (1/Ri - 1/Rf) where G = gravitational constant M₁ = mass of one object M₂ = mass of the other object Ri = initial distance Rf = final distance ΔPE = -ΔKE The Attempt at a Solution My solution is v = 2√(GM/d). I am making sure it is...

Homework Statement A 400-N child is in a swing that is attached to a pair of ropes 2.00 m long. Find the gravitational potential energy of the child-Earth system relative to the child’s lowest position when (b) the ropes make a 30.0° angle with the vertical Homework Equations Ug=mgy The...

Homework Statement Two neutron stars are separated by a distance of 4.80 E 10 m. They each have a mass of 3.60 E 30 kg and a radius of 1.30 E 5 m. If they are initially at rest... How fast is each star moving when their separation has decreased to half its initial value? How fast is each star...

This pertains to a homework question but I get the concept of PE or U = -GmM/a for an elliptical orbit. I also understand the derivation of the total energy of an object in an elliptical orbit as E = -GmM/2a. However, I have a homework question that asks for the ratio of an object's kinetic...

Homework Statement An 18.5kg box is slid up a 5.6m long ramp that makes an angle of 33 degrees with the floor. What is the gravitational potential energy of the box relative to the floor? Homework Equations Ek = 1/2mv2 The Attempt at a Solution My teacher gave me an answer of 550J, but I'm...

Hi everyone I'm kinda new here, your support will really be appreciated ! :D 1. Homework Statement Let's say the cylinder has radius R, and height T. Homework Equations U = ∫GmdM/x The Attempt at a Solution My attempt is shown in the picture, I took a tiny element of the cylinder with...

Homework Statement I am writing a lab report and I need to calculate the uncertainty error for Gravitational Potential Energy and Kinetic Energy. The Professor told us that the margin of uncertainty for time is +- 0.025 seconds, margin for height is +- 0.001 meters, margin for mass is +-0.001...

Homework Statement Why is the gravitational potential energy of a ball a distance r from the center of the Earth negative? Homework Equations U_\text{grav}(r) = - GMm/r [/B] (To me, this makes sense because gravity is an attractive force and bodies will want to minimize the distance between...

I got a little bit confused while studying gravitational potential energy, particularly the expression for long distances: (-GMm/r). An exercise asks me for the velocity, period and radial acceleration for a 1000kg satellite that I wish to put into orbit. That's okay. But after that, I'm...

So say I had a glass of water on a table ,with the glass filled to the top. The bottom of the glass, the water would have a higher pressure than the top of the glass. This is the concept of hydrostatic pressure etc. But how does GPE fit into all of this? Does the water at the top of the glass...

Hello, here's a questions I was wondering if any of you could solve. I don't have the exact numbers, but the scenario is this: a guy standing on the Earth throws a ball upwards and catches it a few seconds later. How does would affect the potential energy and/or mechanical energy of the...

This is the gravitational potential energy formula $$U = -\int_\infty^r\vec{F}_\text{field}\cdot d\vec{r}$$ If r vector's direction is form infinity to r, then it means it has same direction as Gravitational Force. So cos0=1 But after multiplication there is a negative sign here: "-GMm" $$U =...

1. Problem A rocket has landed on Planet X, which has half the radius of Earth. An astronaut onboard the rocket weighs twice as much on Planet X as on Earth. If the escape velocity for the rocket taking off from Earth is v , then its escape velocity on Planet X is a) 2 v b) (√2)v c) v d) v/2 e)...

Homework Statement A projectile is fired vertically from Earth's surface with an initial speed of 3.1 km/s. Neglecting air drag, how far above the surface of Earth will it go? Homework Equations KF+UF=KI+UF U=-G(M1m2)/r2 K=1/2mv2 mass of Earth = 5.972E24 radius of Earth = 6371km G=6.673E-11...

Homework Statement For a satellite of mass ##m_s## in a circular orbit of radius ##r_s## around the Earth, determine its kinetic energy K. Homework Equations ## K = \frac {1}{2}mv^2 ## Gravitational potential energy ## U(r) = - \frac {GmM_E}{r}## The Attempt at a Solution My answer is ## K...

Homework Statement [/B] Calculate the gravitational potential energy of the interacting pair of the Earth and a 23kg block sitting on the surface of the Earth. You would need to supply the absolute value of this result to move the block to a location very far from the Earth (actually, you...

Homework Statement Part A: Derive an expression for the energy needed to launch an object from the surface of Earth to a height h above the surface. Part B: Ignoring Earth's rotation, how much energy is needed to get the same object into orbit at height h? Express your answer in terms of...

Homework Statement A broken spaceship is located h=10 km above the center of a large circular thin sheet of unknown dust. The sheet has a radius of R=106 km and a density of σ = 7*1011 kg/m2. The spaceship and the dust attract each other due to the gravitational force. a) Find the initial...

In this case the height of the fall is far to high above Earth to be use PE=mgh. So I'm trying to integrate the inverse square gravitational force over distance. ##\int \frac{GmM_e}{r^2}dr## So I'm confused with respect to another object, specifically the moon, if the max height of the fall...

I understand that GPE is negative, but it does not come out this way when i try to derive it. I took the change in potential energy in bringing a particle from an infinite distance to a distance of b from another particle. ## \Delta U = - \int \vec F \cdot d \vec r ##. Since the...

Homework Statement Forty 2.0kg blocks 20.0cm thick are used to make a retaining wall in the backyard. Each row of the wall will contain 10 blocks. You may assume that the first block is placed at the reference level. How much gravitational potential energy is stored in the wall when the blocks...

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 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...

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? Homework Equations U = -Gm2 / r The Attempt at a Solution The potential energy is the negative of the work done by gravity in...

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...

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...

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...

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...

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...