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question:

A man of mass 70kg rides a bicycle of mass 15kg at a steady speed of 4ms^{-1}up a road which rises 1m for every 20m of its length. what power is the cyclistdeveloping if there is a constant resistance to motion of 20N?

Ans: 250W

My sol'n so far:

Sin∅ = 1/20

in 1second object moves 4m

therefore

1/20 = x/4

x = 0.2m

E_{p}= mgh

=85(10)(0.2)

=170

E_{k}=0.5mv^{2}

= 0.5(85)4^{2}

= 680

E_{k}+E_{p}= 170 + 680

= 850

work done by resistive force = fs

= 20(4)

= 80

W_{cyclist}= [ E_{p}+ E_{k}] + W_{resistive force}

= 680 + 80

stuck

plz help

where am i going wrong

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# Homework Help: Work, energy, power

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