So, my precalculus teacher thinks that a class of about 28 students are all perfect masters of physics, therefore, she assumes that it's totally normal to give us a physics-related word problem -___- (90% of the class isn't involved/will never be involved with physics.) Here's the problem:

David threw a baseball into the air. The function of the height of the ball in feet is h = 80t –16t^{2}, where t represents the time in seconds after the ball was thrown. Use this function to determine how long it took the ball to fall back to the ground.

Can someone help, please? I'm only a high school junior, and my teacher only gave a simple example to help out with this complex problem; the example and question don't even relate to one another the slightest bit.

Help? Thanks.