Water from Old Faithful Geyser shoots upward to a height of about 50 m once every 90 minutes. What must be the pressure in the hot springs below the ground in order for the water to go that high?

Respuesta :

Solution:

Given:

height of geyser, h = 50 m

speed of water at ground can be given by third eqn of motion with v = 0 m/s:

[tex]u^{2} = v^{2} + 2gh[/tex]

putting v = 0 m/s in the above eqn, we get:

u = [tex]\sqrt{2gh}[/tex]                      (1)

Now, pressure is given by:

[tex]\Delta p = \frac{1}{2}u^{2}\rho \\[/tex]        (2)

where,

[tex]\Delta p[/tex] = density of water = 1000 kg/[tex]m^{3}[/tex]

g = 9.8 m/[tex]s^{2}[/tex]

Using eqn (1) and (2):

[tex]\Delta p = \frac{1}{2}(\sqrt{2gh})^{2}\rho[/tex]

⇒ [tex]\Delta p = \frac{1}{2}\rho gh[/tex]

[tex]\Delta p = \frac{1}{2}\times2\times 1000\times 9.8\times 50[/tex] = [tex]\Delta p[/tex] =   490000 Pa

[tex]p_{atm}[/tex] = 101325 Pa

For absolute pressure, p:

p = [tex]\Delta p[/tex] + [tex]p_{atm}[/tex]

p = 490000 - 101325

p = 388675 Pa

Therefore, pressure in hot springs for the water to attain the height of 50m is 388675 Pa