Quadratic Equations

Question

The Height, h meters, of a falling object is related to the time, t seconds, the object has been falling by the formula h = -4.9t^2 + d. Where d meters is the initial height of the object above the ground. The Bankers Hall building in Calgary is 196m tall. Express the time an object takes to reach the ground from this height as an exact number of seconds.

Answer 1

given equation h = -4.9t² + d

for time from top to bottom substitute given values, then rearrange

0 = -4.9t² + 196

=> 4.9t² = 196

=>t² = 196/4.9

=> t = √(196/4.9) = 6.325 or 6 seconds to nearest second