Gravitational potential energy Definition and 292 Threads

Homework Statement A mail bag with a mass 120kg is suspended by a vertical rope 8.0m long. a.) What horizontal force is necessary to hold the bag in a position displaced sideways 4.0m from its initial position? b.) How much work is done by the worker in moving the bag to this position...

Hello. I'm new. I was looking around on the web a bit to find an answer to my problem, and I came across these forums. Gravitational force = -GMm/(r^2) Gravitational force between a small mass (m) and the Earth (M) is zero at a distance of infinity. Any distance smaller than infinity gives...

Homework Statement Two Jupiter-size planets are released from rest 1.30×10^11 m apart. What are their speeds as they crash together? Homework Equations The Attempt at a Solution I have done K_f + U_f = K_i + U_i with K_i being zero because they have crashed together so... K_f + U_f = U_i...

Homework Statement A binary star system has two stars, each with the same mass as our sun, separated by 1.00×10^12 m. A comet is very far away and essentially at rest. Slowly but surely, gravity pulls the comet toward the stars. Suppose the comet travels along a straight line that passes...

Homework Statement a rocket of mass 1.5e6 kg is launched upward from the surface of the Earth (mass Me =5.97e24, radius Re = 6.38 X 10^6m) with a speed of 0.5 x 10^4 m/s. What is the maximum altitude the rocket will reach above the surface of the Earth? Homework Equations 1/2 mv1^2 -...

1. A spring is suspended froma ceiling and a 256 g mass is attached to it and pulled down to stretch the spring by 18.2 cm. THe mass is released and travels through the equilibrium position with a speed of 0.746 m/s. Calculate the force constant of the spring/ 2. 1/2kx^2 = Ee 1/2mv^2 =...

Homework Statement http://img256.imageshack.us/img256/795/untitledpw7.jpg The Attempt at a Solution I know Ug stands for the gravitational potential energy, but I'm not sure what Us and Uint stands for. At initial stage 1, I know the ball has kinetic energy and also has had work...

Homework Statement determine the amount of work required to move a satellite from orbital radius of 2r_e (twice the radius of the earth) to 3r_e, if it has a mass of 500 kg? Homework Equations Find change in Gravitation potential energy and also the change in the kinetic energy The...

I have an idea I would like to analyze but I'm practically ignorant of physics and engineering so I'm hoping you folks can give me some informative feedback. First, something tells me this idea is ridiculously uneconomical and/or impractical, but I'm still curious to find out and it will be a...

I'm confused about the two equations: PE_{G}=G\frac{m1*m2}{r} PE_{G}=mgh When do you use either of these equations? Can these two equations be used interchangeably or not? Also, I think I remember reading somewhere that you need to use the 1st equation when the problem involves large...

why gravitational potential energy is negative?

Homework Statement By considering the gravitational potential energy of an object at the surface , find an expression for the escape speed from the surface and determine its value. Homework Equations GPE= mgh The Attempt at a Solution KE= 1/2* m * v^2 GPE= mgh GPE+ KE = 0...

Pe = Potential energy Ke = kinetic energy i want to clear up some confusion in me... firstly...it is true to say that potential energy transforms into kinetic energy as an object...correct? then the definition of an ORBIT is constantly falling around a planet, non-stop... therefore...

Hi guys...something does not seem right in physics... escape velocity is defined as the initial velocity required by a projectile to rise vertically and just escape the gravitational field of a planet and gravitational potential energy = 0 only at infinity displacement from planet (i.e...

Homework Statement My question is, if your at the top of an apartment building, maybe the 10th floor, and you have a cup of water in your hand or on the table. Does the water have a higher gravitational potential energy than a cup of water at ground level? Homework Equations The...

Homework Statement Tarzan, in one tree, sights Jane in another tree. He grabs the end of a vine with length 20 m that makes an angle of 45 degrees with the vertical, steps off his tree limb, and swings down and then up to Jane's open arms. When he arrives, his vine makes an angle of 30...

I've recently noticed a very simple paradox in semi-Newtonian gravity which seems to say that there must be some rest energy in the field. However, this obviously conflicts with the GR position. I'm wondering if anyone can spare a moment to clarify the resolution of this paradox. In...

1) 2 stars with the mass and radius of the Sun are separated by distance 10R_s between their centers of mass. (where R_s is the radius of the Sun). A 10000kg space shuttle moves along a line between the stars. Draw a graph of the space shuttle's potential energy (as a function of position)...

Forces & Fields (a) calculate the gravatational potential pf a point A on the surface of the Earth (b) what is the gravatational potential of a point B, 1000km above A? (c) How much energy is expended if an object of mass 10kg were to just reach point B from A? I know the eq. for...

A 520 kg object is released from rest at an altitude of 800 km above the north pole of the earth. Ignore atmospheric friction. The speed of the object as it strikes the earth’s surface, in km/s, is closest to: a.3.7----b. 2.7---c.1.9-----d. 4.0------e. 2.3 Conservation of energy, where...

A 5.2 kg particle and a 2.4 kg particle have a gravitational attraction of magnitude 2.3E-12 N. Gravitational potential energy is -4.40e-11J and r=19.03m If you were to triple the distance between these particles, how much work is done by you on the particles? My biggest problem here is...

Hi, I need to calculate the gravitational potential energy of a rocket that's 500km above the surface of Earth (rocket has a mass of 500kg). What formula would I use, and how would I calculate it? Any help is appreciated, Thanks.

A 395 N child is in a swing that is attached to ropes 1.8 m long. Find the gravitational potential energy of the child+Earth system relative to the child's lowest position when the ropes make a 30° angle with the vertical. What I did with this problem is I drew a diagram and then figured that...

Hello all. I'm studying for sat 2 physics but I still don't understand the formula for gravitational potential in outer space. U = -Gm1m2/r Can anyone explain this to me? Particularly why G is negative and r is used instead of r-squared. Newton was such a genius. :bugeye:

I'd be grateful if someone can help me with this problem - Zero, a hypothetical planet, has a mass of 4.4 × 10^23 kg, a radius of 3.2 × 10^6 m, and no atmosphere. A 2.4 kg space probe is to be launched vertically from its surface. (a) If the probe is launched with an initial energy of 7.4 ×...

For the equation: U=\frac{-GMm}{h} Where h is the distance between the center of masses M and m. In Calculus, they teach you derivatives. The derivative of U with respect to h is: dU=d\left(\frac{-GMm}{h}\right) dU=\frac{GMm}{h^2} Which is the gravitational force. Were I to apply this...

Can kinetic energy of a system or gravitational potential energy be negative? I am reading about the two but its very complex and can't seem to describe why.

A 120kg astronaut stands on the surface of an asteroid of radius 600m. The astrunaut leaves the surface with 15J of kinetic energy and reaches a maximum height of 300m above the surface. What is the mass of the asteroid? (Answer: 3.4*1012kg) At the maximum height, all of the kinetic energy...

Question A Skier with a mass of 65.0 kg. Including equipment, starts from rest and accelerates down a slope. The slope is 27.0 m higher at the top than the bottom. The work done on the skier by the kinetic friction is 1.20 x 10^4 J. How would I determine the Gravitational potential energy...

The first artificial satellite to orbit the Earth was Sputnik I, launched October 4, 1957. The mass of Sputnik I was 83.5 kg, and its distances from the center of the Earth at apogee and perigee were approximately 7370 km and 6560 km, respectively. Find the difference in gravitational potential...

Okay I understand somewhat of this topic of grav potential energy but i got stumped on this one question. I am to find the mass of a satellite orbiting Earth with the given variables of (F)(units: kN) which is the force the sattelite attracts the earth, and given the gravitational potential...

Hello. I'm in gr.11 physics, and we are currently working on Kinetic and gravitational potential energy. We have been asked to create a procedure which shows how gravitational potential energy is turned into kinetic energy(afterwards we will do calculations and such showing the relationshi). We...

A climber's gravitational potential energy increases from 14000J to 21000J while climbing a cliff. She expends 18000J of energy during this activity. What is the efficiency of this process? A) 3% B) 39% C) 61% D) 97% Here is what I did. Wpg = ∆Epg = Epg2-Epg1 = 21000-14000 =...

The gravitational potential energy (U) of an object, from some reference point - such as the surface of the earth, is defined as the amount of work required to move the object from the reference point to its position. The force of gravity is given by: F = -\frac{GMm}{r^2} where r is...

EP = mgh as an object moves further and further away, the value of g decreases and approaches 0.. if this is true, then wouldn't potential energy approach 0 as well? According to my book, this is not true, the gravitational potential energy constantly rises the further 'up' you go If...

How much work is done by the moon's gravitational field as a 1000kg meteor comes from outer space and impacts the moon's surface? all I have to do is: U=-\frac{Gm_1m_2}{r} where _{m_1} is the mass of the moon, _{m_2} is the mass of the meteor, and _{r} is the radius of the moon. is that...

I am a little puzzled by the following: The moon in causing Earth tides causes the Earth to generate heat loss due to friction and slows down the Earth rotation. This decreases the angular momentum of the earth. The angular momentum of the Earth and moon system combined cannot change. So the...

can anyone help me with this problem A shaft is drilled from the surface to the center of the earth. Make the rather unrealistic assumption that the density of the Earth is uniform. With this approximation, the gravitational force on an object with mass m, that is inside the Earth at a...

A 70.0 kg skier rides a 2860 m long lift to the top of a mountain. The lift makes an angle of 14.8° with the horizontal. What is the change in the skier's gravitational potential energy? What equation would I use to solve this problem?

Hi all, I have a few questions that I'd appreciate some guidance on. There are two identical dust particles:- mass 13ug charge +9.8E-15 C electrostatic potential energy 8.7E-17 J gravitational potential energy 1.1E-24 J The mass is given in the question, the energies I calculated...

Find U, the gravitational potential energy of the object at a distance R from the center of the planet, with the gravitational potential energy taken to be zero when the object is infinitely far away from the planet. Express your answer in terms of R, m, M, and G, the universal gravitational...

Given: g=9.81 m/s^2. A 41.7 kg child is in a swing that is attached to robes 2.16 m long. Find the gravitational potiental energy associated with the child relative to the child's lowest position under the following conditions: B. when the ropes make a 34.7 degree angle with the vertical...