Question

What gauge pressure is required in the city water mains for a stream from a fire hose connected to the mains to reach a vertical height of 15.0 m? (Assume that the mains have a much larger diameter than the fire hose.)

Why is your P2 equal to zero atm, when it is actually supposed to be 1atm since at this point in the water is exposed to air pressure. Is air pressure not 1atm?

Answer #1

Using Bernoulli's theorem at initial and final point

P1 + (1/2)*rho*V1^2 + rho*g*h1 = P2 + (1/2)*rho*V2^2 + rho*g*h2

V1 = speed of water in mains = 0 m/sec (since given that mains have a much larger diameter than the fire hose)

V2 = 0, since given that water reaches a vertical height, So this is max height, and at max height velocity becomes zero

h1 = 0 m, and h2 = 15.0 m, So

P1 + 0 + 0 = P2 + 0 + rho*g*h2

P1 = P2 + rho*g*h2

here P2 is not equal to 0 atm, it's equal to atmospheric pressure, So

P1 = P_atm + 1000*9.81*15.0

P1 = P_atm + 147150

Now since we need gauge pressure at water mains, So

P_gauge = absolute pressure - atmospheric pressure = P1 - P_atm

P_gauge = P_atm + 147150 - P_atm

**P_gauge = 147150 Pa = 1.47*10^5 Pa**

**Please Upvote.**

What gauge pressure in the water mains is necessary if a
firehose is to spray water to a height of 38 m ?
Express your answer to two significant figures and include the
appropriate units.
P = ____ Pa

A 2.54 cm inner diameter hose is connected to a
freshwater pump with a gauge pressure of 3.65 atm. The volume flow
rate at the pump is 2.50 gal/min. The other end of the hose is held
at an angle of 300 above the horizontal at a height of
1.20 m.
Determine the velocity of the water as it exits the hose.
Determine the inner diameter of the hose as the water exits the
hose.
Determine the horizontal distance from...

(a) What is the pressure drop due to the Bernoulli effect as
water goes into a 2.70-cm-diameter nozzle from a 8.90-cm-diameter
fire hose while carrying a flow of 41.0 L/s?
N/m2
(b) To what maximum height above the nozzle can this water rise?
(The actual height will be significantly smaller due to air
resistance.)
m

(a) What is the pressure drop due to the Bernoulli effect as
water goes into a 2.70-cm-diameter nozzle from a 8.90-cm-diameter
fire hose while carrying a flow of 41.0 L/s?
N/m2
(b) To what maximum height above the nozzle can this water rise?
(The actual height will be significantly smaller due to air
resistance.)
m

What is the pressure drop (in N/m2) due to the
Bernoulli effect as water goes into a 2.70 cm diameter nozzle from
a 8.90 cm diameter fire hose while carrying a flow of 35.0 L/s?
N/m2
(b)
To what maximum height (in m) above the nozzle can this water
rise? (The actual height will be significantly smaller due to air
resistance.)
m

(a) What is the pressure drop (in N/m2) due to the Bernoulli
effect as water goes into a 3.50 cm diameter nozzle from a 9.10 cm
diameter fire hose while carrying a flow of 34.0 L/s?
Answer is in unit N/m2
(b) To what maximum height (in m) above the nozzle can this
water rise? (The actual height will be significantly smaller due to
air resistance.)
Answer is in unit m

ADVERTISEMENT

Get Answers For Free

Most questions answered within 1 hours.

ADVERTISEMENT

asked 4 minutes ago

asked 10 minutes ago

asked 23 minutes ago

asked 25 minutes ago

asked 30 minutes ago

asked 40 minutes ago

asked 43 minutes ago

asked 1 hour ago

asked 1 hour ago

asked 1 hour ago

asked 1 hour ago

asked 1 hour ago