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posted by  bua on 8/29/2008 1:58:35 PM  |  status: Live  

physics 16, ch6

Course Textbook Chapter Problem
Classical Physics Physics: Principles with Applications (6th) by Giancoli 6 16
Question Details:
a) If the KE of an arrow is doubled, by what factor has its speed increased?

(b) If the speed is quadrupled, by what factor does its KE increase?

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posted by palmreader on 8/29/2008 2:29:44 PM  |  status: Live
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bua's comment:
"that was cool"
Response Details:
kinetic energy at initial velocity v0:
E0 = 0.5mv02
v0 = √(2E0/m)    

a) for 2E0 = 0.5mv2
          v = √(4E0/m)

∴ v/v0 = 2/√2 = 1.414

the speed is increased by a factor of 1.414

b) for E = 0.5m(4v0)2

∴ E/E0 = 0.5m(4v0)2 / 0.5mv02
           = 16
 
the kinetic energy is increased by a factor of 16
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