Question

the observation deck of tall skyscraper 370m above the street. Determine the time required for a penny to free fall from the deck to the street below. Pls explain with steps

Answer 1

Because we know distance d = 370m, initial velocity (v subscript i) = u = 0 m/sec and using acceleration a = 9.80665 m/s^2 we can solve the first equation for time t.

½ a t²+ ut - d = 0

becomes

½ (9.80665 m/sec²) t²+ (0 m/sec)t - 370m = 0

½ (9.80665 m/sec²) t²+ (0 m/sec)t - 370m = 0

½ (9.80665 m/sec²) t² = 370m

t² = 370m x 2/(9.80665 m/sec²)

t² = 740 x/(9.80665/sec²)

t² = 75.459sec²

t = 8.687 sec OR t = - 8.687 sec

Now to find the final velocity when the penny hits the ground

③ v = u + at

v = 0 m/sec + (9.80665 m/sec²) x 8.687 sec

v = 85.188 m/sec

v = 85.188 m/sec x (60 x 60 sec)/hour x (mile/1600 m)

v = 191.673 mph                                     hope it helps you  

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