Calculating Minimum Velocity for Knocking Down a Burning Building Door

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To calculate the minimum velocity required to knock down a burning building door with a fire hose delivering 40 kg of water per second, a force of 1000 N is needed. The momentum principle indicates that the force exerted by the water is equal to the rate of change of momentum, which can be expressed as 1000 kg-m/s per second. Given that the water does not bounce back, the force exerted on the door can be determined by the equation F = (mass flow rate) x (velocity). By rearranging this equation, the minimum velocity can be calculated as v = F / (mass flow rate). Understanding these principles is crucial for solving the problem effectively.
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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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