Question

Stephanie is a very good soccer player. She can kick a soccer ball with an initial velocity of 21.3 m/sec. The function that represents the height of the ball with respect to time is ℎ (x) = − 4.9 x^2 + 21.3 x . About how many seconds will it take for the ball to hit the ground?

Answer 1

If the ball hit the ground it means that its height is equal to 0. In order to find the time after the ball will hit the ground, we need to find the solution of the equation h(x)=0 which is different to 0.

-4.9x^2+21.3x=0
x(-4.9x+21.3)=0
-4.9x+21.3=0
x=21.3/4.9 = 4.3469 seconds