HomeI Student: r My Account Log Out l Help HW 4 Begin Date: 9/15/2017 1:30:00 PM

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HomeI Student: r My Account Log Out l Help HW 4 Begin Date: 9/15/2017 1:30:00 PMDue Date: 9/22/2017 11:59-00 PM End Date: 9/22/2017 11 59-00 PM 04%) Problem 2: Suppose a car approaches a hill and has an initial speed of 112 kmh at the bottom ofthe hill The driver takes her foot off of the gas pedal and allows the car to coast up the hill Assignment Status Click here for detailed view 33% Part (a) If the car has the initial speed stated at a height ofh friction is negligible? 0, how high in meters, can the car coast up a hill if work done by Grade Summary Potential 90% Submissions Attempts remaining: 10 Problem Status 1 Partial cotan asin acosO atan0 acotansinhO cosh tanh cotanh0 Degrees O Radians (2% per attempt) etailed view 4 Partial 5 Partial END BACKSPACE | tsil CLEAR I give up Hints:for a mai deductor. Hints remaining: If friction Notice there are two ways to do this Feedback: 0 deduction per feedback is not presert, what makes the car slow down? & 33% Part (b) If, in actuality, a 730-kg car wath an initial speed of 112 km h is observed to coast up a hill and ing point, how much thermal energy was generated by friction in J? magnitude of the average force of friction, in nevtons, if the hill has a slope 2 above the horizontal? ai o ie @ #

Explanation / Answer

Given,

Initial speed, v = 112 km/h = 31.11 m/s

Using law of conservation of energy principle,

Kinetic energy = Potential energy

(1/2) m x v2 = m x g x h

0.5 x 31.112 = 9.81 x h

h = 49.33 m

So, height car would be 49.33 m

b) Suppose the work done due to friction be W

Using work energy theorem

0.5 x 710 x 31.112 = 710 x 9.81 x 20.5 + W

W = 200795.85 J

c) Suppose the fricition force be F

F = work done / distance traveled

F = 200795.85 /(20.5/sin(2.4°))

F = 410.17 N

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