Quadratic Functions

Question

If an object is dropped from a height of 85 feet, the function h(t)=-16t^2+85 gives the height of the object after t seconds. Approximately, when will the object hit the ground?

 

A ball is thrown into the air with an upward velocity of 32 feet per second. Its height, h, in feet after t seconds is given by the function (h)t=-16t^2+32t+6. What is the ball's maximum height? How long does it take the ball to reach its maximum height. Round to the nearest hundredth, if necessary.

 

A catapult launches a bolder with an upward velocity of 148 ft/s. The height of the boulder, h, in feet after t seconds is given by the function h=-16t^2+148t+30. What is the boulder's maximum height? How long does it take the boulder to reach its maximum height? Round to the nearest hundredth, if necessary/ 

Answer 1

1st part: the equation for falling motion must reflect the fact that height decreases with time...so acceleration of gravity is negative, and the ball will hit ground at the moment when 16t²=85... Solve for t.

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