Question

A rubber ball is thrown upward with an initial speed of 20 m/s. The approximate height of the ball after t seconds is h(t)=20t-4.9t^2. Determine the time period, to the nearest hundredth of a second, during which the ball is higher than 8 m

Answer 1

find where it is equal to8m.
-4.9t^2+20t=8
Find the solutions, and then h>8 between those values.