Calculating Minimum Velocity for Knocking Down a Burning Building Door

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SUMMARY

The discussion focuses on calculating the minimum velocity required for a fire hose to exert a force of 1000 N on a burning building door. Given that the hose delivers water at a rate of 40 kg per second, the minimum velocity can be derived using the momentum principle. The key equation involves understanding that the force exerted is equal to the rate of change of momentum, leading to the conclusion that the minimum velocity must be 25 m/s to achieve the necessary force.

PREREQUISITES
  • Understanding of Newton's Second Law of Motion
  • Knowledge of momentum and its relationship with force
  • Basic principles of fluid dynamics
  • Familiarity with units of measurement (N, kg, m/s)
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  • Study the concept of momentum in physics, specifically the relationship between force and momentum change
  • Learn about fluid dynamics and how it applies to fire hoses and water flow
  • Explore practical applications of force calculations in emergency response scenarios
  • Investigate the effects of water velocity on impact force in various firefighting techniques
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Firefighters, physics students, engineers, and anyone involved in emergency response planning or fluid dynamics will benefit from this discussion.

alessandro
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Homework Statement



a fire hose is turned on the door of a burning building in order to knock the door down. This requires a force a 1000 N. if the hose delivers 40 kg per second, what is the minimum velocity of the stream needed? assuming the water doesn't bounce back?

Homework Equations





The Attempt at a Solution


1000:40=25
 
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Although you did not show your attempt clearly, it would help if you thought a thousand Newton of force as 1000 kg-m/s momentum gained/lost per second. Since water does not bounce back, it loses all momentum on the door and hence exerts a force.The rate of flow of water is given so could you find force it would exert on the door assuming velocity to be v?
 

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