Question

The observation deck of tall skyscraper 311 m above the street. Determine the time required for a penny to free fall from the deck to the street below. (Make x negative since the penny is falling)

Answer 1

Answer:

8.0 s

Explanation:

The penny is in free fall, so its motion is a uniform accelerated motion with constant acceleration; therefore we can use the following suvat equation:

$s=ut+\frac{1}{2}at^2$

where

s is the displacement

u = 0 is the initial velocity of the penny

t is the time

$a=g=-9.8 m/s^2$ is the acceleration of gravity

The displacement is

s = -311 m

So we can re-arrange the equation to solve for t, the time of flight:

$t=\sqrt{\frac{2s}{g}}=\sqrt{\frac{2(-311)}{-9.8}}=8.0 s$