Question

A 70.-kilogram cyclist develops 210 watts of
power while pedaling at a constant velocity of
7.0 meters per second east. What average force is
exerted eastward on the bicycle to maintain this
constant speed?
(1) 490 N (3) 3.0 N
(2) 30. N (4) 0 N

Answer 1

     The Definition of Potence is given by:

$P=Fv$
 
     Entering the unknowns:

$P=Fv \\ 210=7F \\ F= \frac{210}{7} \\ \boxed {F=30N}$

Number 2

If you notice any mistake in my english, please let me know, because i am not native.