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While driving in the rain at 30 m/s you notice that the raindrops appear to be g

ID: 1529380 • Letter: W

Question

While driving in the rain at 30 m/s you notice that the raindrops appear to be going straight down. After dropping your little sister off at daycare you turn around and drive the opposite direction at the same speed. However now you notice that the rain is making an angle of 35 degrees relative to the ground.

a. What is the angle and the speed of the rain relative to the ground?

b. Is this physically possible, or did Dr. Woodney just make up random numbers for this problem that don't yield physically possible results? (show work)

c. Answer honestly: would you have noticed if we didn't ask? If not, you aren't doing your homework right!

Explanation / Answer

Refer to the drawing,

PA = 30 m/s ; PB = 30 m/s

AB = 30 + 30 = 60

theta = 35 deg

tan35 = AB/OB => OB = AB/tan35

OB = 60/0.7 = 85.71 m/s

tan(alpha) = PB/OB = 30/85.71 = 0.35

aplha = 19.3 deg

OP = sqrt (PB^2 + OB^2) = sqrt (30^2 + 85.71) = 90.81 m/s

Hence, the speed of the rain is, OP = 90.81 m/s and angle = 19.3 deg

b)Yes, its possible.