PLEASE HELP IN PHYSICS!!!?

Question

A bicyclist can coast down a 7.0 degrees hill at a steady 9.5 km/hr .The mass of the cyclist plus bicycle is 85.0 kg . If the drag force is proportional to the square of the speed v , so that Fd= - cv^2 .
 
A) Calculate the value of the constant c.
 
B) Calculate the average force that must be applied in order to descend the hill at 27 km/hr . Ignore other types of friction.

Dr. Watkin,. I presume · Accepted Answer

A) There is no acceleration, so the gravity force down the slope must be equal and opposite to the drag force.
So the drag force is Fd = -m*g*sin(7) = -85*9.81*sin(7) = -101.6N
Fd = -cv^2
In SI units, v = 9.5 / 3.6 m/s = 2.639 m/s

so c = -Fd / v^2 = 101.6 / 2.639^2 = 14.6 N.s^2/m^2

B) v = 27 / 3.6 m/s = 7.50 m/s

Applied force = -Fd = c*v^2 = 14.6 * 7.5^2 N = 821 N

PLEASE HELP IN PHYSICS!!!?

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