Energy ...the basics

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This text is meant to accompany class discussions. It is not everything there is to know about energy. It is meant as a  prep for class. More detailed notes and examples are given in the class notes, presentations, and demonstrations (click here.)
Questions Energy questions for this reading.
Gravitational Potential Energy

There is only one form of kinetic energy, but there are many forms of potential energy. For example there is a potential energy stored in the gravitational field. If you lift a body up, then you are putting energy in the body. Anytime a body is lifted higher than it was earlier then is has potential energy. Physicists refer to gravitational potential as energy of position or energy of height. A body has zero potential when it is as the lowest height of its motion. It has the most at the highest point of its motion. Where the potential energy equal to "zero" is a relative thing.

Practice

What is the same about each of the potential energies in the two animations?

It is at a maximum when the ball is the highest away from the gound.

It is zero at the gound, even if one ground is lower than the other.

 

 

Potential energy due to gravity is determined by the following math expression:

Example 2
  • Question
  • Solution

How much potential energy does the orange have?

Orange Tree

Solution

 

Example 3
  • Question
  • Solution

What is the gravitational potential energy of the car as it moves over the hill?

Car on hill

Solution

The fact that the car is moving does not affect its gravitational potential energy because the equation, "mgh," does not contain a velocity variable.

 

Example 4
  • Question
  • Solution
  • Video Solution

In a pinewood derby contest, a contestant's vehicle starts a the top of a ramp that is 4.0 meters long and placed at a 30 degree angle with the floor. If an entry has a mass of 0.140 kg, then what is the car's potential energy compared to the floor's height?

Solution
 

by Tony Wayne ...(If you are a teacher, please feel free to use these resources in your teaching.)

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