The height, h, in feet of a golf ball above the ground after being hit into the air is given by the equation, h = -16t 2 + 64t, where t is the number of seconds elapsed since the ball was hit. How many seconds does it take for the golf ball to hit the ground?

Question

The height, h, in feet of a golf ball above the ground after being hit into the air is given by the equation, h  = -16t 2 + 64t, where t is the number of seconds elapsed since the ball was hit. How many seconds does it take for the golf ball to hit the ground?

aveline · Answer

When the height is equal to zero, the ball has hit the ground. Therefore,
$$0=-16t^ {2}+64t$$

sw33thearts · Answer

yeah but how many sec does it take to ht the ground

aveline · Answer

We start out by dividing by -16:
$$0=-16(t^ {2}-4t)$$
$$0=t^ {2}-4t$$
$$0=(t)(t-4)$$

This means that either t is 0 or 4.

aveline · Answer

After 0 seconds, the ball has just been hit. But after 4 seconds, the ball hits the ground.

sw33thearts · Answer

so 4 seconds

aveline · Answer

Correct

sw33thearts · Answer

thanks