Question

A golfer hits a ball from a starting elevation of 5 feet with a velocity of 70 feet per second

Answer 1

Answer:

Time, t = 4.5 s

Step-by-step explanation:

The number of seconds t it takes the ball to  hit the green can be represented by the equation :

$-16t^2 + 70t + 5 = -4$

It means that the initial velocity is 70 ft/s. The above equation becomes:

$-16t^2 + 70t + 9=0$

It is required to find the time taken by the ball to land on the ground. It is a quadratic equation. The solution of quadratic equation is given by :

$t=\dfrac{-b\pm \sqrt{b^2-4ac} }{2a}\\\\t=\dfrac{-b+ \sqrt{b^2-4ac} }{2a},\dfrac{-b- \sqrt{b^2-4ac} }{2a}\\\\t=\dfrac{-70+ \sqrt{(70)^2-4\times (-16)(9)} }{2(-16)}, \dfrac{-70-\sqrt{(70)^{2}-4\times(-16)(9)}}{2(-16)}$

t = −0.125 and t = 4.5 s

Time cannot be negative. So, the time taken by the ball to land on the ground is 4.5 seconds.