A basketball official size and weight Is released 100 ft bel

A basketball (official size and weight) Is released 100 ft below the surface of a lake. Estimate the time that the ball reaches the surface of the lake.

Solution

Given vertical displacement y= 100ft

from equations of motions we have y = ut+ (1/2)*gt²

but here initial velocity u = 0

the equaiton becomes y = (1/2) gt²

Here g = 9.81 m/s^2

substitute all values in above equation

100 = (1/2)*9.81*t²

t² = 20387

t =4.515 sec