2. A penny has a mass of about 10grams. The penny falls from a height of 169 m a

Question

2. A penny has a mass of about 10grams. The penny falls from a height of 169 m and,unfortunately lands right on the head of a person standing directlybelow it. A) Neglecting air resistance, what is thespeed of the penny the instant it strikes the person’shead? B) The penny comes to rest on the person’shead after penetrating the scalp a distance of 4.17 mm. Needless to say this didn’t feel very good! Determinethe average force exerted by the penny on the head. C) Aftercalculating the force in part (B), discuss why we use the term“average force” in real life situations such asthis.

Kindly includeexplanations for each steps

Explanation / Answer

height h = 169 m mass m = 10 g = 10 * 10 ^ -3 kg initial velocity u = 0 velocity of the penny when it reaches the head = v accleration a = g = 9.8 m/ s ^ 2 from the relation v ^ 2- u ^ 2 = 2ah                          v = [ 2gh ]                             = 3312.4                             = 57.55 m / s After strike: ----------- Initial velocity v = 57.55 m / s final velocity V = 0 distance S = 4.17 mm = 4.17 * 10 ^ -3 m from the relation V ^ 2- v ^ 2 = 2aS Accleration a = [ V^2 -v^2 ] / 2S                     = - 3.9717*10^5 m / s ^2 magnitude of average force F = ma                                              = 10* 10 ^ -3 * 3.9717* 10 ^ 5                                             = 3.9717 * 10 ^ 3 N

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