Problems 2

Biologybabe679

12th December 2007 - 12:36 AM

A 30%-efficient car engine accelerates the 1500 car from rest to 12 m/s.

used effieciency equation
e= W out/Qh
Qh= input

used delta kinetic energy as work =(.5)m(v)^2, k=(.5)(1500)(12)^2 =86400
got an answer of 2900. its wrong though.

also
A typical photovoltaic cell delivers 4.2×10−3 W of electric energy when illuminated with 0.15 W of light energy.

used e= 4.2e-3/.15
answer=.03 but its wrong, is it suppost to be more complicated or something?

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