Energy ...the basics

REVIEW EXAMPLES

Examples
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.)
 
Example 1
A spring board diver leaves the diving board upwards with a velocity of 9.00 m/s. Use energy to determine the speed of the diver when her center of mass is 2.00 m up from the starting point.

 

This video can be found on YouTube at https://youtu.be/cg5chA9jNKs

 
Example 2
You are talking on the phone to your friend in the apartment below you when you notice a ball traveling up past your window. You know that his window is 1.50 m above the ground and yours is 4.50 m up. This ball keeps passing your window when you take video and use it to calculate the ball’s velocity to be 4.50 m/s. You say to him, “It must be traveling at 10.0 m/s at your window,” and he says, “…more like 6.5 m/s.” Who is correct? (Good thing you are both nerdy and can settle this quickly using energy concepts.)

 

This video can be found online at https://youtu.be/uWPYF3kzygw

 
Example 3

The “Valles Marineris” is the deepest canyon on Mars. Its maximum height to its floor is 10,000 m. (This is 5 times deeper than Arizona’s “Grand Canyon.”) The atmosphere on Mars very, very, thin. Neglecting air resistance, how fast would a 2.5 gram penny be traveling when it hit the floor of “Valles Marineris” if it was dropped from the highest point? (Martian gravity accelerates all objects down at 3.88 m/s2.)

This video can be found on YouTube at https://youtu.be/O_NHOzO8FgA

  

 


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

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