Question

A ball is thrown in the air from a platform at time t = 0 seconds. The height, h(t), of the ball can be modeled as a function of time, t, by the equation h(t) = -16t + 40t + 20. Approximately how many seconds after being thrown will the ball hit the ground?
2.37 seconds


1.25 seconds


2.93 seconds


0.13 seconds

Answer 1

Answer:

Option C is the correct answer.

Step-by-step explanation:

The height, h(t), of the ball can be modeled as a function of time, t, by the equation h(t) = -16t² + 40t + 20

When the ball hits the ground, we have h(t) = 0

                  h(t) = -16t² + 40t + 20 = 0

                    $t=\frac{-40\pm \sqrt{40^2-4\times (-16)\times 20}}{2\times (-16)}=\frac{-40\pm \sqrt{2880}}{-32}\\\\t=\frac{-40\pm 53.67}{-32}\\\\\texttt{t = 2.93s or t = -0.43s}$

Negative time is not possible, so time = 2.93 seconds.

Option C is the correct answer.