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PHGN341: Thermal Physics
Quiz 1
January 18, 2013
1. During a hailstorm, hailstones with an average mass of m and a speed of v strike a car front windshield of area, A, which
is at an angle, θ, with respect to the horizontal. The hailstones strike at an average rate of r and scatter elastically
from the windshield. Assume the car is at rest.
(a) In terms of the quantities given, what is the average pressure the hailstones exert on the windshield?
(b) Evaluate the hailstone pressure for m = 3 g, v = 20 m/s, θ = 30◦ , A = 0.6 m2 , and r = 40 per second, and express
your answer as a fraction of atmospheric pressure (1.01 × 105 Pa).
(c) Now assume the car is traveling at 20 m/s. What is the pressure now?
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