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Super Junior Member
Join Date: Mar 2012
Posts: 10
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a jet of water hits wall normally with a speed v.the pressure on the wall is p.if the speed of the jet of water is 4v ,what is the pressure on the wall? Answer is 16p.but I dunno how to prove it.anyone help to prove this.thanks
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physic
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Member
Join Date: Jan 2007
Posts: 196
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1. Force = rate of change of momentum
2. Mass of water delivered per unit time is proportional to velocity 3. Momentum of water delivered per unit time = mass*velocity 4. Substitute 2 in 3 you get momentum of water delivered per unit time is proportional to square of the velocity, which from 1, says it is proportional to the force/pressure So, we have pressure P proportional to V^2, substituting 4V for V you get 16V. |
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