What is 450240

Roseaukaine · 08-20-2003, 04:19 PM

OK - I know the formula for KE, (Velocity X Velocity X Mass/ 450240) but what EXACTLY is the term for the number 450240 in the equation? I know it is a constant, but I want to know the exact term for it.

98Redline · 08-20-2003, 04:38 PM

Courtesey of Bow Jackson:

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Weight of an arrow; W=mg
where m=mass, g=gravitational constant 32.22 ft/s^2

Mass of an arrow ; m=W/g
but W is measure in grains, convert grains to lbs 1 lb = 7000 grn

m = W(grn)(1lb/7000grn)/32.22 ft/s^2

The basic relationship being used in all calculations is;

Kinetic Energy(KE) = 1/2 * m * v^2 (or one-half times mass(of arrow) times velocity squared)

Normally people just say KE = arrow weight divided by 451,000 something or other times velocity squared, here' s where it comes from;

KE = 1/2 X (arrow weight in grains) X (1 lb/7000grn) X v^2 X (1/32.22)

2 X 7000 X 32.22 = 451,080 grn-ft/s^2 and that' s where that number comes from.

Roseaukaine · 08-20-2003, 08:48 PM

[

][X(]. Ok - that was more than I expected[&:]. I was searching for a word to describe it but that' l do just fine - I guess

.

Arthur P · 08-20-2003, 11:02 PM

Grains divided by 7000 converts grains to pounds. Pounds divided by the gravitational constant converts pounds to mass. There is an ongoing debate about whether the gravitaional constant is 32.16 fps^2 or 32.22 fps^2, but that' s for the physicists to decide.

Multiplying 7000 by 32.16fps^2 gives you 450240. That' s where the 450240 came from.

Deleted User · 08-21-2003, 06:08 AM

[Deleted by Admins]

Arthur P · 08-21-2003, 08:27 AM

LOL!