Question

A waterfall has a height of 1900 feet. A pebble is thrown upward from the top of the falls with an initial velocity of 12 feet per second. The height, h, of the pebble after t seconds is given by the equation h=-16t^2+12t+1900. How long after the pebble is thrown will it hit the ground?

Answer 1

Answer:

Step-by-step explanation:

h is the height of the pebble after a certain amount of time has gone by. Since we are told to find that time when the pebble is on the ground, we say that h = 0 since the height of something on the ground has no height at all. Then factor the quadratic.

$-16t^2+12t+1900=0$

Throw that into the quadratic formula or however you were taught to factor irrational quadratics (maybe completing the square?) to get that

t = 11.27869 sec and t = -10.52869 sec

Since we all know that time will never carry a negative value, we will disregard it and go with 11.27869 seconds. Not sure to where you are told to round.