By landing properly and on soft ground (and by being lucky!), humans have surviv
ID: 2004674 • Letter: B
Question
By landing properly and on soft ground (and by being lucky!), humans have survived falls from airplanes when, for example, a parachute failed to open, with astonishingly little injury. Without a parachute, a typical human eventually reaches a terminal velocity of about 62.0 m/s. Suppose the fall is from an airplane 1000 m high.How fast would a person be falling when he reached the ground if there were no air drag?
(in m/s)
If a 70.0 kg person reaches the ground traveling at the terminal velocity of 62.0 m/s, how much mechanical energy was lost during the fall?
What happened to that energy?(up to 500 words per hw)
Please!! be my lifesaver??!
Explanation / Answer
a) First use the formula Ui +Ki = Uf + Kf, where U is potential energy, and K is kinetic energy.
Now, you know that he starts on top, so Ki is 0, and because he hits the ground you know Uf is zero. So you would get
Ui = Kf, where Ui = mgh and Kf = mv2/2, solve for v and you will get
v = (2gh) , because the masses would cancel out.
v = (2*9.81*1000) = 140.07 m/s
b) To find how much mechanical energy was lost, just minus the potential energy by the kinetic energy.
Elost= (70)(9.81)(1000) - (70)(62)2/2 = 686700 - 134540 = 552160 J lost, which I believe was lost due to the air drag on the way down.
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