03.3 You fly an airplane to a city that is 800 miles to the west and 300 miles t
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03.3 You fly an airplane to a city that is 800 miles to the west and 300 miles to the north of your starting point. The wind is blowing from east to west. Your plane has an airspeed of 200 mph and the trip takes 3.55 hours. a) In what direction did you aim the plane? b) What is the speed of the wind? 03.4 When walking on a moving sidewalk in the same direction the sidewalk is moving, you take 24 s to go the length of the sidewalk. When walking on the sidewalk in the opposite direction to its motion, you take 36 s to return to your starting point. Your walking speed on fixed ground is 1.5 m/s. How long is the moving sidewalk and how fast is it moving?Explanation / Answer
3.4
Suppose length of moving sidewalk is d
Speed of moving sidewalk = V1
your speed = Vy
when you are moving in same direction as sidewalk, then
Vnet = V1 + Vy
Vnet = V1 + 1.5 m/sec
time taken = t1 = d/Vnet
t1 = d/(V1 + 1.5) = 24
d = 24*(V1 + 1.5)
when you are moving in opposite direction as sidewalk, then
Vnet = Vy - V1
Vnet = 1.5 - V1 m/sec
time taken = t2 = d/Vnet
t2 = d/(1.5 - V1) = 36
d = 36*(1.5 - V1)
from both equations
24*(V1 + 1.5) = 36*(1.5 - V1)
60*V1 = 36*1.5 - 24*1.5
V1 = 18/60 = 0.3 m/sec
d = 24*(0.3 + 1.5)
d = 43.2 m
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