please help me!!

Question

A projectile was projected into the air off a rooftop with an initial velocity at 32 feet per second. The quadratic equation h=-16t^2+32t+240 represents the height, h, of the projectile t seconds after it was projected into the air. According to the equation, how many seconds should it take for the projectile to hit the ground

Answer 1

Ok if we have an equation that tells us the height of the projectile  when it is t seconds, that means we can easily find the seconds it should take.

 

For example at 0 seconds the height is 240 feet. If we replace t with 0 you get that h=240.

So when it hits the ground the height will be what???

 

It should be 0 because the ground is technically 0 feet, or just no height.

 

So if H is 0 what is t?

 

This will involve using the quadratic equation,

 

x=(-b±√b²-4ac)/2a

the a,b c comes from the equation given,

ax²+bx+c=0

a=-16

b=32

c=240

 

(you can actually simply this if you divide your a,b,c by 16. Then just plug it in into the equation i wrote)

instead of X we are using T

 

T=(-32±√32²-4(-16)(240))/2(-16)

 

So you get

T=(-32+128)/-32==>this becomes T=-3 Seconds

or

T=(-32-128)/-32==>this becomes T=5 Seconds

 

Since time cannot be negative the answer is 5 Seconds.

 

(Warning I'm 65% sure this is the answer, Haven't done physics in a while, GOOD LUCK)