posted by Nick .
If a bicyclist of mass 68.0 kg (including the bicycle) can coast down a 7.00° hill at a steady speed of 6.20 km/h because of air resistance, how much force must be applied to climb the hill at the same speed (and the same air resistance)?
Weight component downhill = air resistance at 6.2 km/h
(You know that from the constant coasting speed)
When going uphill at the same speed, the uphill force must equal the sum of the weight downhill component and the air resistance. That sum will be TWICE the weight component downhill.
F = 2 M g sin7 = 81.2 N