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Homework Statement
I can't figure this one out. I can't use any of Newtons laws to solve this, kinetic formulas, and w=Em+Ek doesn't seem to be working for energy. I know the answer, but I can't solve it.
kg = kilogram
m/s = meters per second
m = meter
A 0.002kg bullet is traveling at 87 m/s, after passing through a 4 cm block of wood its speed is 12 m/s.
a) How much work is lost due to friction (Answer is -7.4 J but I can't solve it mathematically)
b) Average force of block (Answer is -180 N)
Homework Equations
a) For work lost due to friction I'm guessing they want to know the air resistance, I have no idea how to do this part
b) Average force of block:
wcd = (.5*12^2)-(.5*87^2) = -3 712.5 J
P = w/t but the only problem is no time is supplied. I'm not quite sure what to do
The Attempt at a Solution
a) .5 * 87^2 = .5 * 12^2