word problem help please!

Question

A waterfall has a height of 1100 feet. A pebble is thrown upward from the top of the falls with an initial velocity of 24 feet per second. The height of the pebble h in feet after t seconds is given by the equation h=−16t2+24t+1100. How long after the pebble is thrown will it hit the ground?

Answer 1

Hi,

The way to understand the problem is to draw a diagram.

(it is a parabola opening downwards.)

The function, h(t) describes the height of the pebble at time, t.

The pebble will hit the ground means, h(t)=0.

Solve the function setting h(t)=0 or graph and find the zero (only the positive value: time is positive)

 

You should get the time to be, t= 9.075 minutes.