Question

When WIll This Rocket Hit the Ground

y = -5t^2+25t+10

Answer 1

\[y = -5t^2+25t+10 \]
=
\[h=-(5t+2)(t-5)\]

Answer 2

I have gotten the factored form but what Do I do from here to find when it lands ?

Answer 3

the answer is 5 seconds but I got 5.4 beacuse should we subtrace the tw x-intercets?

Answer 4

The answer says the rocket will land after 5 seconds but shouldnt it he 5.4 because we need to consider both x-intercets

Answer 5

Pay attention to the negative sign.

Answer 6

\[\Large h=-(5t+2)(t-5) = 0\]You don't subtract the two t values. You just solve that for both t values, one of which will be negative, one positive. One is the t value when it hits the ground. Does it make sense for time to be negative?

Answer 7

Solving that gives the x-intercepts, well t-intercepts really. When h=0, that means height is zero, thus it hits the ground.

Answer 8

We did a similar question in class where the path of water from a water spout was
-(d-1)(d-5) and in this case to find the distance traveled (not time) we subtraced 5 -1 giving 4 so thats what made me think to subtract here

Answer 9

h = -(d-1)(d-5)

Answer 10

We aren't finding distance travelled, though. We're finding the time when it hits the ground.

Answer 11

Also what If both the x-interceptsd were positive?

Answer 12

for time?

Answer 13

But I can't figure out where you got those factors. Because they do not multiply back. Did you post the problem incorrectly or something?

Answer 14

h = -d^2+6d-5

Answer 15

d would be distance, t is time, two different variables.

You wouldn't get two positive - that would mean the object hits the ground twice (doesn't make much sense), or it's not fired at t=0.

And @Mertsj is right, your factoring isn't correct.

Answer 16

So time cannot have two positive x-intercepts?

Answer 17

you guys are right, my factoring is wrong