hey friends how are you? i need help in two physics problems..plz i mstuck here..thnx guys?

Question

1) blood is pumped out of the heart via thick walled(2mm) tube known as the aorta(inside diametere about 18mm) at an average speed for adult at rest, of 0.33m/s.
a)compute the discharge rate
b)the aorta branches into about 32 majotr arteries that are each roughly the same size-namely- 4mm inside diametere. detrmine the speed of blood through these arteries.(HInt:- it is diffrent thn if there were just one!)

2) a uniform solid cube of material 10 cm on each side has a mass of 700 g.
b)if so, how much of its volume will be submerged?

Answer 1

1 A. The cross sectional area of the interior of the aorta is (9mm)^2 * (pi). That's 81 * (3.14159) or about 255 square mm. With a speed of 330 mm the volume is 84150 cubic mm/second. Or about .084 liters/second.

1 B. The TOTAL cross sectional area of the 'branches' is 24 * 2^2 * 3.14259. The ratio of the diameters is 81/96. So the speed is 81/96 * .330, or about .278 m/sec.

2. The mass is 700 grams. The mass of an equivalent volume of water is 1000 grams. The cube would only displace 700 grams of water. So, 300 CCs would remain above water. 700 ccs would be below water.