Question

When a ball is thrown upward, the formula h=-16t^2+64t gives its height h (in feet) above the ground after t seconds. How many seconds does it take for the ball to strike the ground?

Answer 1

solve for t wen h = 0 :P

Answer 2

i dont know how to do that :(

Answer 3

-16t(t-4) = 0

Answer 4

then?

Answer 5

solve that equation using the zero product property...

Answer 6

16t=0 and t=4

Answer 7

because when the ball hits the ground height=0

Answer 8

im lost :(

Answer 9

-16t(t-4) = 0
wen t = 0 r t-4 = 0
u get t= 0 r 4 ok?

Answer 10

lol im kind of slow , can u write out the equation so i can solve it?

Answer 11

ok, when the ball hits the ground, the height is 0 because the ball is on the ground, so make the equation equal to zero and the factor it out as shown above. You will have two solutions since you have a t^2 which will be 16t=0 and t=4

Answer 12

\[16t ^{2}+64t= 16t(t+4)=0\]
Now your values will be t=0 and when t=-4 but since time can't be negative, it's t=0 only.

Answer 13

actually its 16t(t-4) and then you have t=4 and t=0 apologies..

Answer 14

i still dont get it but i'll figure something out, thanks .

Answer 15

cmon.......u need time wen ball hits the ground r8

Answer 16

Ok assume you throw a ball upwards, it will get to a maximum height and then it will come down again right? This is how it's path would look like
Forming a parabola. So when the ball comes back down, and hits the ground the height of the ball will be zero since it's on the ground. So to find the time it takes to hit the ground, we find the time when the height is equal to zero. So you just put h as o and solve for t. Factoring out -16t and then you would have -16t(t-4) = 0 Equations of such form give you two answers, 16t=0 which is just t=0 and t-4=0 which is t=4
I hope that helps.

Answer 17

i get it now thanks ! it was much easier when i put it into my graphing calculator :) @beeqay