2.5 m 35° Figure 6.23 The skier\'s initial kinetic energy is partially used in c
ID: 1792562 • Letter: 2
Question
2.5 m 35° Figure 6.23 The skier's initial kinetic energy is partially used in coasting to the top of a rise. Problem 28. 6.30 (a) How high a hill can a car coast up (engine disengaged) if friction is negligible and its initial speed is 110 km/h? (b) If, in actuality, a 750 kg car with an initial speed of 110 km/h is observed to coast up a hill to a height 22.0 m above its starting point, how much thermal energy was gen- erated by friction? (c) What is the average force of friction if the hill has a slope 2.5° above the horizontal? Explicitly show how you follow the steps in the Problem-Solving Strategy for energy found on pages 159 and 160. Section 6.7 Power 6.31 The Crab nebula pulsar is the remnant of a supernova that occurred in A.D. 1054. Using data from Table 6.2, calculate the annroximate factor hy which the nower outnut of thiExplanation / Answer
a)
vi=110km/hr = 110000m/3600s = 30.56m/s
By law of conservation of energy,
PEf=KEi
mgh=1/2mvi^2
h=v^2/2g
h=30.56^2/(2*9.8)
h= 47.65 m
b)
Ethermal = PEf – KEi
Ethermal = mgh-1/2mvi^2
Ethermal = 750*9.8*22 – ½*750*30.56^2
Ethermal = 1.88*10^5 J
c)
Ethermal =Ffriction *d
Ethermal =Ffriction *hsin
Ffriction =Ethermal / hsin
Ffriction = (1.88*10^5)/(22sin2.5)
Ffriction =1.96*10^5 N
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