If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

## Middle school physics - NGSS

### Course: Middle school physics - NGSS>Unit 3

Lesson 2: Potential energy

# Potential energy

Potential energy is type of stored energy that an object or system of objects may have based on their size, shape, position, or even material they are made from. Learn about what potential energy is and the different types of potential energy an object may have. Created by Khan Academy.

## Video transcript

- [Narrator] Hello, everyone. Let's talk about potential energy. Potential energy is energy that is stored in an object, and this energy is related to the potential or the future possibility for an object to have a different type of energy, like kinetic energy for motion, that is converted from that potential energy. There are many kinds of potential energy, but they all arise from an object's relation to a position, or an original shape. So while in general, there are many different types of potential energy, there are several specific types that are very common. So, let's talk about these. Gravitational potential energy is the potential energy that an object with mass has due to the force of gravity from another object with mass, like say, the Earth. And in fact, we often use the surface of the Earth to compare an object's position with to see how much potential energy it has in the Earth's gravitational field. Gravity is an attractive force, so objects with mass want to move towards the surface of the Earth. If we move them further away, or opposite the direction of the gravitational force, we increase their gravitational potential energy. And the opposite is true if it gets closer. When an object is on the surface of Earth, we typically say it has no potential energy, but you could use any point to be this comparison where potential energy is zero. Consider a book on a bookshelf. If the book is on this shelf, we can use this shelf as the 0.4 potential energy. Moving it to a higher shelf would mean it has gravitational potential energy relative to that lower shelf, or relative to the floor if we want to use that as our comparison instead. Next, we have elastic potential energy, which is the potential energy some objects have due to their shape being changed. These types of objects are called elastic objects. Elastic objects are made of materials and designed, so they have internal or inside forces that try to return them to their original shape. One very common example of this is a spring. When you stretch or compress a spring, you change its shape. And the shape of the spring causes internal forces that try to return the spring to its original shape. Now electric potential energy, which is the potential energy a charged object has due to the electric force from another charged object. Opposite electric charges are attracted to one another, and similar electric charges are repelled. So the potential energy depends on what type of charges there are, and how far apart they are. Potential energy increases when the charges move opposite the direction of the electric force, for example, when two negative charges get closer together. Similarly, magnetic potential energy is the potential energy a magnetic object has due to the magnetic force from another magnet. Magnetic force causes similar poles to repel one another, and opposite poles to attract. And because magnets have north and south poles, the potential energy depends not only on the position within a field, but also the magnets orientation. Again, you could increase the potential energy by moving the magnets opposite the direction of the magnetic force. For example, by pulling apart a North Pole and a South Pole. All of these types of energy are due to different forces, and are calculated differently from different equations, which we won't cover here, but they are all potential energy. And these are just a few of the most common types of potential energy, but there are more. In summary, potential energy is the stored energy in an object due to its position, its properties, and the forces acting on it. Potential energy is measured relative to some comparison position or shape, and describes the potential for other forms of energy, commonly kinetic energy for motion, to exist. There are many forms of potential energy, including gravitational, elastic, magnetic, and electric. Thanks for watching, and I hope you learned a little bit of something.