A bike creates 50 N of frictional force on the ground. How much force would you need to keep the velocity of the bike constant

Asap and show ! a 14 kg rock starting from rest free falls through a distance of 5.0 m with no air resistance. find the momentum change of the rock caused by its fall and the resulting change in the magnitude of earths velocity. earth mass is 6.0 * 10^24 kg. show your work assuming the rock earth system is closed.

What are two different ways you could find the value of a? explain these methods.

This is for my 8th grade science class, i really don’t understand. can someone me? , lol.