A ball is thrown vertically upward from the ground. Its distance from the ground after t seconds is given by s(t)=16t^2+176t After how many seconds will the ball be 128 feet from the ground?

Answer 1

Hello Anastasia,

the distance is given to you by the equation s(t) = 16t² + 176t

"After how many seconds will the ball be 128 ft from the ground?" means finding t such that s(t) = 128

That is: 16t² + 176t = 128

Subtract 128 from both sides: 16t² + 176t - 128 = 0

All the coefficients are actually multiples of 16, so you can divide by 16 ----> t² + 11t - 8 = 0

You can solve this equation using the quadratic formula. You will get 2 solutions. One will be negative, the other will be positive. Since time can't be negative, you will choose the positive solution as your answer.

Cheers!