# Kinetic Energy

Discussion in 'Bowhunting' started by telkev, May 16, 2008.

1. ### telkevActive Member

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May 17, 2007
I have forgotten and lost the formula for finding kinetic energy, does anyone have it handy?

2. ### EagletWell-Known Member

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Feb 2, 2005
KE=(1/2)mV²where m = mass of object
v = speed of object
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For a bullet it goes like this:

Formula used:
Energy = 1/2* weight * velocity^2 / 7000 / 32.175

Where weight is in grains, and velocity is in feet/second.

7000 is grains per pound to convert the bullet weight
into Lbs; and 32.175 is acceleration due to gravity.
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Or we can just say:

Energy = weight * velocity^2 / 450450

450450 comes from (7000*32.175*2)=450450
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Example:
Bullet = 117 gr. MV=2900 ft/sec
Energy = 2900*2900*117/450450 = 2184.4 ft/lbs
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3. ### telkevActive Member

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44
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May 17, 2007
Thanks, I feel stupid, I have used that formula so much in the past, I didn't even need a calculator. Guess I know which brain cells didn't make it.

4. ### EagletWell-Known Member

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Telkev,
don't mistreat yourself like that, I went to take an engineering test for a job, 3½ hours and in one of the question I needed the formula for a sphere's volume and I just could not remember it. And that I have used more than the KE formula. Starts happening after 40. LOL