# Physics

A cup of mass m, placed on the edge of a table of height h, has potential energy mgh, where g is the acceleration due to gravity. Someone slams a door, causing the cup to fall to the floor. If h = 100 cm, what is the approximate speed of the cup when it hits the floor?

(Note: Answer: 4.2 m/s. Show the steps in your solution. For such a short fall, you may neglect air resistance. To simplify the numerical part of the calculation, you may use the following approximations: g ! 9.0 m/s/s and "2 ! 1.4)

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1. The kinetic energy will equal mgh

1/2 mv^2=mgh
v= sqrt(2gh) where h is in meters.
I am somewhat surprised that this question was given in a physics class. Who in the world would approximate g as 9m/s^2? Silly, silly, silly. Why not approximate 1meter as 94cm? or a kilogram as 920grams? or a mile as 5000 feet?, or as done in one state, legally defince PI as 3, instead of 3.14... , after all, it does simplify calculations.

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2. CHEM7300 Assignment?

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posted by Mark D.

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