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Saturday, October 1, 2016

Physics Problem with Solution - Average Power Output

What is the average power output of an engine when a car of mass M accelerates uniformly (a=const) from rest to a final speed V over a distance d on flat, level ground?
Ignore energy lost due to friction and air resistance.
Derive a formula for average power P in terms of variables: the mass M, the final speed V, and the distance d.
P
=P(M,V,d) ?

Solution:
Pₐ=W/t
K-Kₒ=W
Kₒ=0
KMV²
PₐMV²/t
V=at
d=½at²= ½Vt
t=2d/V


Pₐ=½MV²/t=½MV²/(2d/V) = ¼MV³/d

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