i need a little help on this problem and i'm not sure if i have the equation down right.(adsbygoogle = window.adsbygoogle || []).push({});

a 1990kg car accelerates uniformly fromrest to a speed of 17.1 m/s in 4.21 sec.

now the question states what is the instantaneous power delivered by the net force to the car at 2s. answer in units of w.

so this is what i did.

i know that the equation is P=dw/dt which is F*v

to find F i did F=ma but i need to find out what a is

vf=vi+at

vf=vi+at

17.1m/s = 0 m/s + a(2s)

a = 8.55 m/s

F = 1990kg (8.55m/s) = 17014.5

then i plug all that into P= F*v

P = 17014.5 * 17.1 m/s = 290947.95

but thats wrong (online submit). my instructor told the class that v in that equation is the final velocity. am i doing something wrong here. i already found the average power in for the 4.21s and i already found work done.

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# Homework Help: Instantaneous power problem

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