Question

A student drops a ball off the top of building and records that the ball takes 4.70s to reach the ground. Determine all unknowns and answer the following questions. Neglect drag.What was the ball's speed just before striking the ground?From what height was the ball dropped?

Answer 1

In order to determine the speed of the ball just before striking the ground, use the following formula:

$v=v_o+gt$

where

g: gravitational acceleration constant = 9.8 m/s^2

vo: initial speed = 0 m/s

t: time = 4.70s

Replace the previous values of the parameters into the formula for v:

$v=0\frac{m}{s}+(9.8\frac{m}{s^2})(4.70s)=46.06\frac{m}{s}$

Hence, the speed of the ball is 46.06 m/s

The height from the ball was dropped can be obtained by using the following formula:

$y=y_o-v_0t-\frac{1}{2}gt^2$

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