Shape of the water bell formed by the jets.

A fountain consists of a small hemispherical rose (sprayer) which lies on the surface of the water in a basin, as illustrated in the figure. The rose has evenly distributed small holes in it, through which water spurts at the same speed in all directions.

What is the shape of the water bell formed by the jets?

Source: 200 PPiP

13 Answers

1
Arshad ~Died~ ·

i think the water bell will be somewhat like a cylinder......i think

1
rickde ·

look like parabola or more like a branch of a hyperbola

66
kaymant ·

The shape is a paraboloid of revolution.

1
Arshad ~Died~ ·

sir,
what is a "paraboloid of revolution" ???

62
Lokesh Verma ·

Yes it is a paraboloid..

Hint:

Think of a section..

1
rickde ·

i was thinking 2-d
it is a paraboloid

62
Lokesh Verma ·

if you can just prove for the 2D, the quesiton is solved.. [1]

1
rickde ·

ok now this was actually my friend's idea...

we see the shape will be either parabola or hyperbola

the water droplet coming out at 45° will have longest range

so the shape of the water bell formed near the end will be decided by the path of this water droplet
and it is that of a parabola
if the shape was like hyperbola then the path near the end must tend towards a tangent(i.e. its asymptote)
but as the end is part of a parabola we can never get asymptote

hence it is a parabola

1
rickde ·

i think i couldnt explain properly

62
Lokesh Verma ·

Not at all..

infact what you have shown is the trajectory of each "sprinkle" from the water bell..

What you have to show is the final shape of the whole thing..

I mean each of the sprinkles will have a "envelope"

You have to find the equation of that ...

1
rickde ·

to finish off this thread

the trajectory of droplet is
y=x tan\theta - \frac{1/2gx^2}{u^2}sec^2\theta

maximum y for a given x will be at

tan\theta=\frac{u^2}{gx}

so we get

y_{env}=x\frac{u^2}{gx}- \frac{1/2gx^2}{u^2}\left(1+\frac{u^4}{g^2x^2} \right)

hence equation of envelop of jet is

y_{env}=\frac{u^2}{g}- \frac{1/2gx^2}{u^2}\left(1+\frac{u^4}{g^2x^2} \right)

1
rickde ·

am i rite now bhaiya...............

66
kaymant ·

That's correct. To make it clear, the equation is
y=\dfrac{u^2}{2g}-\dfrac{g}{2u^2}\,x^2

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