1. The pressure in the atmosphere is not constant, but fluctuates as the weather changes. If the pressure outside a window drops by 6% while the pressure inside does not change, what is the force on the window? Assume the area of the window is 1.1 m2.
(The positive direction is toward the inside of the window. Indicate the direction with the sign of your answer. Assume that the initial pressure inside and outside the window is initially 1 atm.)

2. Consider a rectangular swimming pool of depth 2.4 m with a width and length of 17 m. What is the force exerted by the water on one of the sidewalls of the pool?

3. An engineer is given the job of designing the water system for a tall building. He decides to locate the pumps at ground level and feed the entire building from there. If the top floor of the building is 278 m above ground level, what must the pressure be at pump level?


4. A blood vessel is 23 cm long and has a radius of 1.7 mm. If blood is flowing through it with a volume flow rate of 2.2 10-7m3/s, what is the difference in the pressures at the two ends of the blood vessel?


5. A platinum sphere of radius 6.8 mm is dropped into a lake. What is the terminal speed of the sphere?


75fg per correct answer

1)
atmospheric pressure is 101,325 Pascals, or 101,325 Newtons per meter squared.

Pressure drops by 6% on the outside, and the pressure on the inside stays constant.

The pressure differential is 0.06*101325 = 6079.5 Newtons per meter squared, multiply by 1.1 meters squared which is the area of the window

F = 6687.45 N toward the outside, since toward the inside is positive, the answer should be negative.

F = -6687.45N.

2)
Force exerted on the wall would be the integral from 0 to 2.4m of g*rho*L*ydy, which g, rho, and L being constants you simply multiply them by 2.4^2/2
Density of water is 1000 kg/m^3, g = 9.81 m/s^2, L = 17m, 2.4^2 = 5.76
1000*9.81*17*5.76/2 = 480297.6 N
http://www.youtube.com/watch?v=f06Q3O3sMm4 Use this video if you need a full explanation.

3)
P = rho*g*h -> assume both top and bottom have the same ambient pressure, so you only need to solve for the differential relative pressure
P = 1000 * 9.81 * 278
P = 272,718 N


This post was edited by Dontrunaway on Nov 21 2013 10:22pm

#1 correct, sent fg

#2 and #3 are coming up incorrect

This post was edited by g4mer on Nov 21 2013 10:22pm

5)
Density of platinum is 21.45 g/cm^3, radius = 6.8 mm -> Volume = 4/3pir^3 = 1317.09 mm^3 = 1.31709 cm^3 -> mass = 28.2516 grams = 0.0282516 kg
Density of water is 1000 kg/m^3

vterminal = sqrt(2mg/CrhoA) where C = 0.5 for spheres
A = 4pir^2 = 0.58107 m^2

Checking units: kg * m/s^2 * m^3/kg /m^2 = m^2/s^2 which is expected

vterminal = sqrt(2*0.0282516*9.81/0.5/1000/0.58107)
vterminal = 0.043679 m/s

Seems incredibly too low, so check it over to see if you find any mistakes.

#4 and #5 incorrect

This post was edited by g4mer on Nov 21 2013 10:59pm

My initial guess for 4 would be zero if the vessel is horizontal. The only thing that would account for a pressure differential would be if it were vertical and there was a height difference between the two ends of 23 cm.

The pressure differential would then be equal to rho*g*h. Since the area is constant I'm not entirely sure why they gave you a velocity other than to maybe throw you off.

Density of blood is 1060 kg/m^3, g = 9.81 m/s^2, h = 0.23m. Pressure differential would be 2391.678 Pa, or 2.391678 kPa if the vessel is vertical.

There is no other feasible answer unless you left something off.



Beyond my help then. Hard doing this shit in a text box as it is. gl

This post was edited by Dontrunaway on Nov 21 2013 11:03pm

assignment time limit is over, fg for answers no longer stand