What Is the Rate of Change of Momentum When Water Hits a Building?

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SUMMARY

The discussion centers on calculating the rate of change of momentum when water from a fire hose hits a building. The problem states that 2528 gallons of water per minute strikes the building at a velocity of 28 m/s. The correct approach involves converting gallons to kilograms, resulting in 159.5 kg of water per second. The momentum change is calculated by multiplying this mass by the velocity, leading to a momentum change of 4466 kg·m/s. However, the user is advised to double-check their arithmetic for accuracy.

PREREQUISITES
  • Understanding of momentum and its formula (momentum = mass × velocity)
  • Knowledge of unit conversions, specifically from gallons to liters and liters to kilograms
  • Basic arithmetic skills for calculations
  • Familiarity with the concept of rate of change in physics
NEXT STEPS
  • Review the principles of momentum in physics
  • Practice unit conversion techniques, especially for fluid measurements
  • Explore examples of momentum change in real-world scenarios
  • Learn about the implications of momentum in collision physics
USEFUL FOR

Students studying physics, particularly those focusing on mechanics and momentum, as well as educators seeking to clarify concepts related to fluid dynamics and momentum calculations.

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Tried this problem, but not getting it.

Homework Statement


A fire hose sends 2528 gallons of water per minute against a building. The water strikes the building at 28 m/s and does not bounce back. What is the magnitude of the rate of change of momentum of the water?

Homework Equations


The Attempt at a Solution


I used the conversion factor of 1 gallon / 3.7856 L and 1 kg / 1 L to find how many kg of water per minute. Then divided by 60 to find how many kg of water per second. I got 159.5 kg of water per second. Then I multiplied by the velocity to get 4466, but I did not get it correct. Am I on the right track or missing something? PLEASE HELP!
 
Last edited:
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You seem to be doing it correctly. Check your arithmetic once more.
 

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