What Determines the Kinetic and Potential Energy Levels in a Punted Football?

[amandamolegir]

Homework Statement

A football is punted downfield (neglect the resistance of the air.)
a.) Where in the path of the punted ball is the kinetic energy the greatest?
b.) where in the path of the punted ball is the potential energy the greatest?
c. Where in the path of the punted ball is the mechanical energy the greatest?
d.) When the return man catches the ball what happens to the kinetc energy that the ball had?

Homework Equations

none that i know of

The Attempt at a Solution

a.) is it at the top when its thrown
b. is it when its about to be kicked?
c. i don't know this one
d. is this there is no kinetic energy?

 

[LowlyPion]

What is the potential energy formula for an object at any height?

 

[amandamolegir]

i don't know.. I don't think i ever learned that...

 

[LowlyPion]

i don't know.. I don't think i ever learned that...

OK. Well time to learn that then

PE = m*g*h

So at what h in the flight of the ball is PE at its max?

 

[amandamolegir]

at the highest point?

 

[NBAJam100]

at the highest point?

yes.

Now to get #1 think about how PE and KE are related. When KE is at a min, where is the PE? When KE is at a max, where is the PE?

 

[amandamolegir]

when KE is at a minuimum, there isn't much motion...So the potential energy would be greater...
So when Ke is at a max, PE would be lower

 

[NBAJam100]

when KE is at a minuimum, there isn't much motion...So the potential energy would be greater...
So when Ke is at a max, PE would be lower

youre certainly on the right track here.

So you found that PE is greatest when the ball is at its maximum height. So when do you think its KE would be highest keeping in mind what you just concluded?

 

[amandamolegir]

also at its highest point

 

[NBAJam100]

also at its highest point

How could that be so? You determined this already:

"So when Ke is at a max, PE would be lower"

So how can the KE in this situation be at a max when PE is at a max?

If I were you, before you go any further look up some information on projectile motion.

http://www.ac.wwu.edu/~vawter/PhysicsNet/Topics/Vectors/ProjectilesMotion.html

Here is a very basic set of equations and a diagram. Dont limit your search to this, do some of your own research on projectile motion