Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.
Trending News
PLEASE HELP IN PHYSICS!!!?
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.
1 Answer
- 9 years agoFavorite 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
