Force to hold nozzle with given flow rate and velocity

Click For Summary
SUMMARY

The discussion focuses on calculating the force required to hold a fire hose nozzle stationary while discharging water at a rate of 16.0 kg/s and a speed of 20 m/s. The correct approach involves using the momentum formula, where momentum (p) is defined as mass (m) multiplied by velocity (v). The force needed to counteract the momentum change is determined to be 320 N, calculated as the product of the mass flow rate and the velocity of the water discharged (16.0 kg/s * 20 m/s). The initial miscalculation involving gravity was clarified as unnecessary for this scenario.

PREREQUISITES
  • Understanding of momentum (p = mv)
  • Basic knowledge of impulse and force
  • Familiarity with Newton's laws of motion
  • Concept of mass flow rate in fluid dynamics
NEXT STEPS
  • Study the principles of fluid dynamics and mass flow rate
  • Learn about Newton's second law of motion and its applications
  • Explore the concept of impulse and its relation to momentum
  • Investigate real-world applications of force calculations in firefighting equipment
USEFUL FOR

Students studying physics, engineers working with fluid dynamics, and professionals in firefighting or hydraulic systems will benefit from this discussion.

kt102188
Messages
3
Reaction score
0

Homework Statement



A fire hose discharges water at a rate of 16.0 kg/s with a speed of 20 m/s. What magnitude of force is needed to hold the nozzle stationary?

Homework Equations



Impulse= Change in Momentum, Momentum (p)= mv, velocity final=velocity inital + at

The Attempt at a Solution



V= 20m/s + 9.81m/(s*s)= 29.81
M=(16.0kg)(29.81)
=476.96

Since impulse is the force over time, I thought impulse should be the force needed to keep the hose stationary, but it's not. Any help in where I went wrong would be great! Thanks!
 
Physics news on Phys.org


Well, first of all I don't see why you're calculating in gravity. Remember, you're only interested in the force as soon as it exits the fire hose.

So, the momentum would just be the mass discharged per second times the velocity of the discharged mass (16*20)
I took the beginning of physics froma really bad teacher and as such spent my calss time talking to my girlfriend and ignoring the class, so I'm fuzzy but it seems that that should be your answer.
 

Similar threads

Bernoulli equation / fluid flow / finding height
  • · Replies 6 ·
Replies
6
Views
3K
Mechanics -- Converting volumetric flow rate to nozzle velocity
  • · Replies 6 ·
Replies
6
Views
5K
Work done during a collision -- Change in Kinetic Energy & change in Momentum
  • · Replies 1 ·
Replies
1
Views
2K
Maximum height for water from a fire hose
  • · Replies 4 ·
Replies
4
Views
4K
Impulse question given flow rate (litres per second)
  • · Replies 19 ·
Replies
19
Views
2K
How Does Impulse Relate to Momentum Change in Physics Problems?
  • · Replies 7 ·
Replies
7
Views
2K
Speed/Velocity and Volume Flow Rate of Viscous Fluids
  • · Replies 5 ·
Replies
5
Views
2K
Force required to hold a fire hose
  • · Replies 13 ·
Replies
13
Views
20K
Calculating Force Exerted by Water at Nozzle
  • · Replies 21 ·
Replies
21
Views
4K
Momentum: instantaneous or average?
  • · Replies 9 ·
Replies
9
Views
1K