| MadSci Network: Physics |
Greetings: Wind is not a force it is a momentum vector ( momentum (p) = mass (m) multiplied by velocity (v) ). To produce a force something must stop or redirect the wind. So this problem is an impulse and momentum problem. The impulse (force multiplied by time = the horizontal momentum before hitting the plate minus the horizontal momentum after hitting the plate). F x t = [m(before) x v(before)] – [m(after) x v(after)] If we take the time (t) to be one second then we can obtain the force and if v(after) is parallel to the plate then v(after) in the horizontal direction = 0 and the momentum in the horizontal direction = 0 Thus simplified for the conditions above: F = m(before) x v(before) For a 50 mph wind, in one second, the force would be proportional to: F = m(before) x 50 = 50 x m For a 250 mile/hr wind the mass flow in one second would be 5 x m(before) and the force would be proportional to: F = 5 x m(before) x 250 miles/hr.= 1250 x m Therefore F(250mph) = 25 times F(50mph) To get the actual values for the forces in pounds (English units) you need to convert the velocity to feet per second and the air mass to slugs per second. Also, the reduced pressure behind the plate caused by the airflow patterns would have to be considered to obtain an accurate answer. Best regards, Your Mad Scientist Adrian Popa
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