Answer: 2.5 seconds.
Step-by-step explanation:
Hi, since when the ball hits the ground the height = 0, to answer this question we have to substitute h=o in the equation:
h = - 4.9t2 - 35t +120
0 = - 4.9t2 - 35t +120
Applying the quadratic formula:
For: ax2+ bx + c
x =[ -b ± √b²-4ac] /2a
Replacing with the values given:
x =[ -(-35) ± √(-35)²-4(-4.9)120] /2(-4.9)
x = [ 35 ± √1,225 +2,352] /-9.8
x = [ 35 ± √3,577] /-9.8
x = [ 35 ±59.8 ] /-9.8
Positive:
x = [ 35 + 59.8] /-9.8 = 94.8 /-9.8 = -9.67 seconds
Negative:
x = [ 35 - 59.8] /-9.8 = -24.8 /-9.8 = 2.5 seconds
Since the time can't be negative, the answer is 2.5 seconds.
Feel free to ask for more if needed or if you did not understand something.
