Homework 5 Begin Date: 2/13/2018 12:00.00 AM-Due Date: 3/7/2018 11:59.00 PM End
ID: 1583635 • Letter: H
Question
Homework 5 Begin Date: 2/13/2018 12:00.00 AM-Due Date: 3/7/2018 11:59.00 PM End Date: 3/7/2018 11:59.00 PM (6%) Problem 7:1f a car takes a banked curve at less than a given speed, friction is needed to keep it from sliding toward the inside of the curve (a real problem on icy mountain roads). 50% Part (a) Calculate the minimum speed, in meters per second required to take a s 4 m radius curve banked at ise so that you d slide inwards, assuming there is no friction. 50% Part (b) what is the minimum coefficient of friction needed for a frightened driver to take the same curve at 18 kmh? Grade Sum Potential Submissions Amempts rem detailled vier sin0 cotan) atan() cosho coso asin) tan0n acoso 45 6 acotan( ) ODegrees Radians l give Hints:deduction per hint. Hints remang Feedback: doduction er feodback. Submission History Answer Feedback 0.279 Totals 0%Explanation / Answer
(b)Given
v = 18 km/h = 5 m/s
theta = 18 deg ; R = 84 m
we know that
v = sqrt {rg[sin(theta) + us cos(thets)]/[cos(theta) - us sin(theta)]}
or
v^2 = {rg[sin(theta) + us cos(thets)]/[cos(theta) - us sin(theta)]}
5^2 = 84 x 9.8 (sin18 + us cos18)/(cos18 - us sin18)
25/84 x 9.8 = (0.31 - us 0.95)/(0.95 - us 0.31)
0.03 (0.95 - us 0.31) = (0.31 - us 0.95)
0.0285 - us 0.0093 = 0.31 - us 0.95
us (-0.0093 + 0.95) = 0.31 - 0.0285 = 0.2815
us = 0.2815/0.9407 = 0.299
Hence, us = 0.299
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