Question

A bicyclist rides with a constant velocity of 8 m/s. What would you need to know to calculate the net force on the rider?

Answer 1

zero                     acceleration would be your answer

Answer 2

You already have everything you need to know.

As soon as you heard "constant velocity", you knew that his speed is constant
and he's moving in a straight line. At that moment, the Physics section of your
brain called out "zero acceleration !", and you knew that the net force on him
must be zero.