ladder, leaver her stranded. She knows that a high wind reduces the air pressure on the roof, and that there is a danger for the pressure inside the house will blow the roof off. As the wind reaches a speed of 30m/s, she calls her Auntie Em for help. Calculate the force on the roof.
Looks like you need to use Bernoulli’s equation which is, er….
the sum of kinetic energy, pressure x volume and gravitational potential energy = constant.
so it must be something like
v^2/2 + p/d + gh = constant
v = velocity, p = pressure, d = density, g = gravitational acceleration, h = height.
velocity of air in the house is zero.
the pressures are unknown, but you only need the difference between inside the house and outside. If necessary assume 1 atmosphere for the air in the house.
height is approximately the same on the two surfaces of the roof so you can ignore this term.
That should be enough to solve it.
November 30th, 2009 at 12:39 am
nice try. are u looking for help with ur physics homework? sorry i did that 11 years ago. it hurts my brain having to figure this out. hope someone else can help.
References :
November 30th, 2009 at 12:54 am
Looks like you need to use Bernoulli’s equation which is, er….
the sum of kinetic energy, pressure x volume and gravitational potential energy = constant.
so it must be something like
v^2/2 + p/d + gh = constant
v = velocity, p = pressure, d = density, g = gravitational acceleration, h = height.
velocity of air in the house is zero.
the pressures are unknown, but you only need the difference between inside the house and outside. If necessary assume 1 atmosphere for the air in the house.
height is approximately the same on the two surfaces of the roof so you can ignore this term.
That should be enough to solve it.
References :