# What is the formula for gravitational potential energy?

### VERIFIED

### Peter Jones

Experienced and passionate tutor, and recent PhD recipient

Gravitational potential energy is a tricky concept. The GPE of an object of mass m at a distance r from another object of mass M is: U = - GmM/r where G is Newton's gravitational constant. This gives you the absolute value of GPE, which you study in A-level physics. Often we are interested in the *change* in GPE when moving an object through a height h. This is what you study at GCSE for example, and in AS. If the object with mass m moves from a distance r to a distance (r+h) away from the mass M then we can use the above formula to find the change in GPE: Change in GPE = - GmM/(r+h) + GmM/r If you are close to the surface of the earth then you can take r=R (radius of earth) and h is much much smaller than R. In this case, some A-level maths can convince you that the above formula reduces approximately to: Change in GPE = mgh where g= GM/R ~ 9.81, and this is the formula we all know and love.

### VERIFIED

### Usman Mohammed

Maths and Physics just got a whole lot easier...

GPE = mass x gravitational field strength x height Mass of the object is usually measured in kg. Gravitational field strength is a measure of โhow strong gravity isโ. On Earth it is 10 (N/kg) and on the moon it is about 2(N/kg). Height is the distance we move the object. We usually measure this in metres.

### Answers from these tutors

### Asked in Physics ๐

ASKED BY LEXI

PHYSICS ๐#### A toy car slides down a slope. If the top of the slope is 2m higher than the foot of the slope, how fast will the car be moving when it reaches the foot? (Assume that all of its g.p.e is transformed to k.e?

Hi! In this question, we can use the change in gravitational potential energy to calculate the kinetic energy that the car will have at the foot of ...

ASKED BY DANIEL

PHYSICS ๐#### What is the difference between intermolecular forces and bonds?

Intermolecular forces are the forces that hold two or more molecules together. A chemical bond is an attractive force between two or more atoms....

ASKED BY MAAHUM

PHYSICS ๐#### Can you please explain the motor effect, generator effect and dynamos in physics?

The motor effect: Creating a force(movement) by passing a current through a conductor in a magnetic field The generator effect: Creating a current i...

ASKED BY HAJAR

PHYSICS ๐#### What energy store is decreasing while the candle is burning?

The fuel for burning is the wax which is constantly decreasing once it is turned into vapour it combines with the air oxygen to form the flame. ...

ASKED BY MYP.PHE EDIFY

PHYSICS ๐#### A train travels 700 km in 35 secs. What will the speed be meters per second?

Average speed is 700000/35 = 20000 m/s Unrealistic as it is approx 58 times the speed of sound !!!

ASKED BY DAISY

PHYSICS ๐#### What happens when an atom is ionised?

An atom becomes ionised when it becomes charged. This charge can be positive (+) or negative (-). What generally causes this is the gain or loss of ...

ASKED BY CARMEN

PHYSICS ๐#### Theory of relativity for startups - how does that work?

Special relativity: This is based on two assumptions. 1. Laws of physics are the same in all inertial frames. 2. Speed of light is the same for all ...

ASKED BY JAKE

PHYSICS ๐#### How do you calculate theoretical deflections for an experiment on unsymmetrical bending of a cantilever beam & what are the units to be used for young's modulus, length, force and 2nd moment area of used for the equation used to calculate deflection?

All this depends on the cross section of the cantilever and how it is supported then you build the theoretical model. Units of Youngโs Modulus are P...

ASKED BY DEBBIE

PHYSICS ๐#### How big is our galaxy?

The average radius of our galaxy, The Milky Way, is about 50,000 light years. To put that in perspective, if a commercial airliner, letโs say a Boei...

ASKED BY DEEPESH

PHYSICS ๐#### What is chemical effect of electric current? Describe it briefly?

So electrical energy can be used to produce chemical reactions. The best example for this is electrolysis. When an electrical current flows through ...

Find me a tutor

We take your privacy seriously. View our policy.