- #1

BurpHa

- 44

- 13

- Homework Statement
- A fire hose held near the ground shoots water at a

speed of 6.5 m / s. At what angle(s) should the nozzle point

in order that the water land 2.5 m away?

- Relevant Equations
- X = V0 * t + 1/2at^2. t = 2V0y / 9.8

We know the time it takes the water complete the whole parabola is (sin(x) * 6.5 * 2) / 9.8.

So I come up with (sin(x) * 6.5 * 2) / 9.8 * cos(x) * 6.5 = 2.5, because the x component of the velocity is the same for the whole time.

But I get the results like these: x≈0.30929171+πn,1.26150461+πn.

I see the correct results are x=72.27889027+180n,17.72110972+180nx

When I use t = 2.5 / cos(x) * 6.5 and plug it in 0 = sin(x) * 6.5 * (2.5 / cos(x) * 6.5) - 4.9 * (2.5 / cos(x) * 6.5) ^ 2, I get the desired results.

I don't know what is not right in (sin(x) * 6.5 * 2) / 9.8 * cos(x) * 6.5 = 2.5 that gets me wrong.

So I come up with (sin(x) * 6.5 * 2) / 9.8 * cos(x) * 6.5 = 2.5, because the x component of the velocity is the same for the whole time.

But I get the results like these: x≈0.30929171+πn,1.26150461+πn.

I see the correct results are x=72.27889027+180n,17.72110972+180nx

When I use t = 2.5 / cos(x) * 6.5 and plug it in 0 = sin(x) * 6.5 * (2.5 / cos(x) * 6.5) - 4.9 * (2.5 / cos(x) * 6.5) ^ 2, I get the desired results.

I don't know what is not right in (sin(x) * 6.5 * 2) / 9.8 * cos(x) * 6.5 = 2.5 that gets me wrong.