quadratic function (word problem)

Question

A ball is thrown up in the air from the ground and follow the function h(t) = 50t - 4.90t² where t is time in seconds. what is the total time the ball stays in the air.

 

I need help in answering the questions, I don't know how to carry out the problem and when I try I just get tangld in a web of numbers and wrong answers

Answer 1

h(t) = 50t - 4.90t² = t(50 - 4.90t)

 

When h(t) = 0, the ball is on the ground.  Note that

 

t(50 - 4.90t) = 0 ⇒ t = 0 or t = 50/4.90 =10.20

 

t = 0 or 10.20

 

t = 0 is the instant of launch from the ground, so t = 10.20 has to be the time the ball returned to the ground.  Then its total travel time in the air is 10.20 seconds.

Answer 2

Find the x-intercepts of h(t).  Then you will take the difference between the t-values.  That difference will be your time lapse in the air.

 

I am wondering if you did this.