Ask Science describes the difference and relationship of potential and kinetic energy via a scene in the movie Kung Fu Panda.
You’ve probably heard people say things like, “John sure has a lot of potential.” Or perhaps you’ve heard the slightly less complimentary, “John just isn’t living up to his potential.” You can probably infer from such statements the idea that John has the capability of doing something awesome, but isn’t quite doing it yet. That’s exactly what potential energy is: energy that has the capability to do something awesome, but isn’t quite doing it yet.
And in the spirit of awesomeness, today we’re going to talk about potential energy and its close twin, kinetic energy, by taking a look at one of my favorite movies, Kung-Fu Panda.
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There Is No Charge for Awesomeness
I’m going to assume that you’ve seen the movie, and if you have kids and own the movie I’ll assume that it’s been played at least a dozen times in your house. Regardless of how many times you’ve seen it, hopefully you remember the scene where Po, the panda, is attempting to gain entry into the temple to witness the selection of the new Dragon Warrior.
After a long, hard climb up the steps to the monastery, Po is rewarded for his hard work with a locked door. He makes several attempts to enter through alternative means, all of which involve potential and kinetic energy, but I just want to focus on the one that finally works: the rocket chair.
The Love Hate Relationship of Potential Energy
Let’s take a moment to define potential and kinetic energy, along with their relationship. Whenever something is doing something, kinetic energy is involved. Movement, sound, heat, light, electricity, are all forms of kinetic energy.
Potential energy is the energy that is stored up waiting to become kinetic energy. If you stretch a rubber band for example, you have filled it with potential energy. When you let go of the rubber band, the potential energy turns into kinetic energy as the rubber band sails (hopefully) away from you.
There’s a special relationship between potential and kinetic energy called the law of conservation of energy. The law of conservation of energy says that within a closed system, the amount of energy doesn’t change; it just changes from one form to another. Now, let’s go back to Kung Fu Panda to see some examples of this law in action.
An Explosive Chair
Po’s rocket chair consists of a bamboo chair with a bunch of fireworks strapped on the sides. His hope is that the fireworks will propel him into the air, over the monastery wall, and into the monastery. The fireworks have chemicals in them that will burn when ignited. Those chemicals store potential energy in the form of their chemical bonds. When activated by heat, the chemical bonds change, and the potential energy stored within them is converted into the kinetic energy that is used to launch the firework into the air. (We’ll ignore for now just how powerful a set of fireworks you’d need to launch a 300-pound panda.)
As the fireworks climb upward, some of their chemical potential energy is converted into movement, some into light, some into heat, and some into sound.
What Goes Up, Must Come Down
As Po travels upwards, the kinetic energy of his movement is converted into another form of potential energy, gravitational potential energy. The amount of gravitational potential energy an object has is proportional to its mass and height. So the larger the mass of the object, or panda, and the higher up it goes, the more gravitational potential energy it stores up.
See also: Bowling and the Conservation of Momentum
Eventually Po’s rocket power runs out and he begins to fall back to the Earth. As he does so, the gravitational potential energy is converted back into the kinetic energy of his descent. When he hits the ground, the kinetic energy of his movement is converted wind, sound, and heat, resulting in a small explosion.
So now you know the difference between potential energy and kinetic energy, as well as the relationship between the two. You also know the slightly less practical bit of knowledge of how to get a panda into a locked Kung Fu monastery.
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Po image from Shutterstock