1. If you drop a penny off the Empire State Building (height of 381m) how fast w

Question

1. If you drop a penny off the Empire State Building (height of 381m) how fast will it be going when it hits the sidewalk below ignoring air resistance? Note you can't ignore air resistance in this case, the penny reaches its terminal velocity of about 20m/s not the velocity you get without air resistance 2. If you throw a baseball straight up into the air at 8m/s how long will it take to come back down to your hand? Ignore air resistance. 3. If you want to knock an apple out of a tree 12m above you, how fast must you throw a rock in order to hit the apple? Ignore air resistance.

Explanation / Answer

1. Applying vf^2 - vi^2 = 2 a d

v^2 - 0^2 = 2(-9.8)(0 - 381)

v = 86.4 m/s .....Ans

2. as it come back then yi = yf = 0

Applying yf - yi = v0y t + ay t^2 / 2

0 - 0 = (8 t) + (-9.8 t^2 / 2)

t = 1.63 sec

3. vf^2 - vi^2 =2 ad

0^2 - v0^2 = 2(-9.8)(12 - 0 )

v0 = 15.4 m/s

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