# Physics

posted by on .

this one is kind of hard

A bicyclist can coast down a 7.0 degree hill at a steady 9.5 h^-1 km. If the drag force is proportional to the square fo the speed v, so that Fd = cv^2, calculate

(a) the value fo the constant c and

(b) the average force that must be applied in order to descend the hill at 25 h^-1 km. The mass of the cyclist plus bicycle is 80.0 kg. Ignore other types of friction.

ok for (a) I got 6.7 x 10^-13 m^-1 kg

for (b) I am completly lost the way it's put you would assume there to be zero acceleration so how are you suppose to solve (b)???

• Physics - ,

wait I think i got it lol
can you tell me if my answer for (a) is right???

• Physics - ,

• Physics - ,

ok how is this for (a)

8.2 x 10^-14 m^-1 kg

• Physics - ,

ok for (a)

13.719 m^-1 kg

• Physics - ,

ok with correct sig figs (a)

13.7 m^-1 kg

• Physics - ,

ok i'm stuck on part (b)

• Physics - ,

part b ...
a velocity of 25 h^-1 km

is it constant velocity were there would be no acceleration if so then there would be no net force...

so i'm lost

• Physics - ,

ok for (a)

13.7 s^-1 kg

• Physics - ,

for (b) i got

-.4172 N ;[

• Physics - ,

ok I know this is right I redid it

(a) 13.7 m^-1 kg

• Physics - ,

ok for b i got 565 N which was correct with book answer in back

• Physics - ,

constant speed....so force drag=force gravity

mg*sinTheta=cv^2

check that.

• Physics - ,

ok for drag force

c = v^-2 Fgx = (2.639 s^-1 m)^-2 95.5 N

Fgx = mg sin theta