A hunter wishes to cross a river that is 2.4 km wide and flows with a speed of 5

Question

A hunter wishes to cross a river that is 2.4 km wide and flows with a speed of 5.0 km/h parallel to its banks. The hunter uses a small powerboat that moves at a maximum speed of 12 km/h with respect to the water. What is the minimum time necessary for crossing? min Need Help? A car travels due east with a speed of 44.0 km/h. Raindrops are falling at a constant speed vertically with respect to the Earth. The traces of the rain on the side windows of the car make an angle of 48.0 degree with the vertical. Find the velocity of the rain with respect to the following reference frames. (Enter the magnitude of the velocity.) the car m/s the Earth m/s Need Help?

Explanation / Answer

2)
It doesn’t matter how fast the river flows!...
If he aims straight across relative to the river he will travel the shortest distance across so T=D/V
T = 2.4 km/12 km/hr
T = 0.2 hrs
T = 12 minutes --> Answer

3)
44 km/h = 12.222 m/s
tan(48) = 12.222 m/s/x
--> x = 12.222 / tan48
where is is the vertical velocity of the raindrop (= relative to earth)
v = 11.004 m/s <--- velocity relative to earth--> Answer to b)

v relative to car is = vector sum of both velocities
v = (12.222^2 + 11.004^2) = 16.45 m/s <-- velocity relative to car--> Answer to a)

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