posted by Morgan
A bicyclist is coasting straight down a hill at a constant speed. The mass of the rider and bicycle is 80 kg and the hill is inclines at 15 degrees with respect to the horizontal. Air resistance opposes the motion of the cyclist. Later, the bicyclist climbs the same hill at the same constant speed (so same force of air resistance). How much force (directed parallel to the hill) must be applied by friction to the bicycle in order for the bicyclist to climb the hill?