Originally Posted by spasm3

15 degree. That angle absorbs less energy and allows the hailstone to continue moving imparting less energy to the glass. Seems to me the closer you get to 90 degrees, the more energy is absorbed by the glass.

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- Thread starter MolaKule
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Originally Posted by spasm3

15 degree. That angle absorbs less energy and allows the hailstone to continue moving imparting less energy to the glass. Seems to me the closer you get to 90 degrees, the more energy is absorbed by the glass.

Originally Posted by spasm3

Too add to my previous post, think of a stone skipping on the water vs dropping straight down in to the water.

Originally Posted by Gebo

Originally Posted by spasm3

15 degree. That angle absorbs less energy and allows the hailstone to continue moving imparting less energy to the glass. Seems to me the closer you get to 90 degrees, the more energy is absorbed by the glass.

Originally Posted by zorobabel

Are the windshields identical in size?

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Glad to see many responses and thanks to all who submitted answers.
Those who started their analysis with a horizontal windshield had the right idea. A horizontal windshield would receive the full energy of impact, whereas the more we tilt it toward the vertical the less the impact energy the windshield would receive, If the windshield were purely vertical the vertical component of impact energy would be zero.
For impact studies of this type we assume a purely elastic collision where there is no mass exchange of the two bodies at collision nor are there any frictional forces involved. I.e., Energy is conserved. Both bodies are thus solid bodies.
A free falling hailstone is limited to a certain velocity because of the aerodynamic drag on the surface of the mass.
Hail with a free fall velocity of 91 feet/second (27.34 m/s) has an impact energy of 7.25 ft.lbs or 9.83 N.m.
If we use a bit of trig, (the sine of the angle of tilt or slope) we can determine the total impact energy for any angle of tilt or slope.
For a 15 degrees slope the impact energy would be Kimpact 15 degrees = 0.26X7.25 ft.Lbs = 1.88 ft.lbs (2.6 N.m) of energy.
For a 30 degrees slope the impact energy would be Kimpact 30 degrees = 0.5X7.25 ft.Lbs = 3.63 ft.lbs (4.9 N.m) of energy.
So the windshield with a tilt of 30 degrees would have the higher probability of being damaged because it would receive the greater impact energy..
For a fully horizontal impact, at 90 degrees the impact energy would be Kimpact 90 degrees = 1X7.25 ft.Lbs = 7.25 ft.lbs or 9.83 N.m.
For the same reason, roof shingles on highly sloped roofs receive less damage than shingles on less sloped roofs. The difference here is that in hail collisions with roofs, some of the energy is absorbed by the shingle (an "inelastic" collision), so it takes a larger hailstone to damage asphalt shingled roofs.

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Originally Posted by Gebo

So the "hardness" of the hail is irrelevant? Interesting ðŸ¤”

Quote

For impact studies of this type we assume a purely elastic collision where there is no mass exchange of the two bodies at collision nor are there any frictional forces involved. I.e., Energy is conserved. Both bodies are thus solid bodies.

Originally Posted by Gebo