A juggler tosses a ball into the air. The ball leaves the juggler's hand 3 feet above the ground and has an initial velocity of 20 feet per second. The juggler catches the ball when it falls back to a height of 4 feet. How long is the ball in the air?

You are standing next to a really big circular lake. you want to measure the diameter of the lake, but you don't want to have to swim across with a measuring tape! you decide to walk around the perimeter of the lake and measure its circumference, and find that it's 400\pi\text{ m}400? m. what is the diameter dd of the lake?