A circus clown at the top of a 60-foot platform is playing catch with another clown on the ground.
The clown on the platform drops a ball at the same time as the one on the ground tosses a ball upward at 80 ft/sec.
For what length of time is the distance between the balls less than or equal to 10 feet?
Hint: the initial velocity of a ball that is dropped is 0 ft/sec.
The formula for the height S in feet above the earth at a time t seconds for an object projected into the air with an initial velocity of v ft/sec from an initial height of s0 is:
S = -16t2 + v0t + s0