(606) Problem 16: Suppose a car approaches a hill and has an initial speed of 10
ID: 2031888 • Letter: #
Question
(606) Problem 16: Suppose a car approaches a hill and has an initial speed of 104 km/h at the bottom of the hill. The driver takes her foot off of the gas pedal and allows the car to coast up the hill 33% Part (a) If the car has the initial speed stated at a height of h = 0, how high, in meters, can the car coast up a hill if work done by friction is negligible? Grade Summary Deductions Potential 090 100% sin0 coso cotansi acosO atan acotan O coshtanh cotanh tan ( Submissions Attempts remaining: 1 (0% per attempt) detailed view 0 Degrees Radians Submit Hint I give up! Hints: 2% deduction per hint. Hints r emaining:4 Feedback: 290 deduction per feedback. 33% Part (b) If, in actuality, a 710-kg car with an initial speed of 104 km/h is observed to coast up a hill and stops at a height 22.5 m above its starting point, how much thermal energy was generated by friction in J? 33% Part (c) what is the magnitude of the average force of friction, in newtons, if the hill has a slope 2.3° above the horizontal?Explanation / Answer
a)
By Conservation of energy
(1/2)mV2=mgho
(1/2)*(104*1000/3600) =9.81*ho
ho=42.54 m
b)
From Work energy theorem
W=(1/2)mV2-mgh =(1/2)(710)(104*1000/3600)2-710*9.81*22.5
W=1.4*105 J
c)
Average force of friction
F=W/d =1.4*105/(22.5/sin2.8)
F=303 N
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