Problem 5.69 Constants | Periodic Table Part A A bicyclist can coast down a 4.0

Question

Problem 5.69 Constants | Periodic Table Part A A bicyclist can coast down a 4.0 hill at a steady 9.0 km/h .The mass of the cyclist plus bicycle is 70.0 kg. If the drag foroe is proportional to the square of the speed 1, so that Fr Calculate the value of the constant c Express your answer using two significant figures. Submit Previous Answers Request Answer X incorrect: Try Again: 5 attempts remaining Part B Calculate the average foroe that must be applied in arder to descend the hill at 27 km/h Ignore other types of friction. Express your answer using two significant figures. Subrmit Request Answer

Explanation / Answer

Given,

mass, m = 70 kg,

g = 9.8 m/s^2,

theta = 4°

v = 9 km/h = 2.5 m/s

A) When bicyclist moves down the inclined plane we get

m g sin theta - F = 0

m g sin theta = cv

c = (m g sin theta) / v = (70 * 9.8 * sin 4°) / 2.5 = 19.14 kg/s

B) The average force that must be applied in order to descend the hill at 27 km/h is

Fnet = m g sin theta - F

= cv - m g sin theta

v = 27 km/h = 7.5 m/s

F = (19.14 * 7.5) - (70 * 9.8 * sin 4°) = 95.70 N

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