Problem 4 (6.25 pts): A grain of pollen has a radius of approximately 15 microns (1.5 x 107 m) and a mass of ap- proximately 1.7 x 107! kg. Calculate the terminal speed of a pollen grain falling down to the bottom of a lake. The viscosity of water is 6.5 x 10~* kg/m-s. A) 164 x 1072 m/s B) 0.9 x 107 m/s C) 34 x1072 m/s D) 9.5 x 1071 m/s Problem 16 (6.25 pts): Imagine that plaque buildup obstructs 1/4 of the area of one of your arteries (so that 3/4 remains open to flow). According to the Hagen-Poiseuille equation, by how much does the flow rate change, assuming your body maintains the same pressure difference: A) @ increases by a factor of 1.78 B) @ drops by a factor of 0.75 C) @ drops by a factor of 0.56 D) @ drops by a factor of 0.25 E) @ only drops by a factor of 0.063 Problem 13 (6.25 pts): Parts of an artery can get blocked with fatty deposits as shown schematically below: Since the volumetric flow remains constant along the length of this tube, how does the flow speed at the narrowest part of this artery compare to the flow speed in the widest part? A) Flow speed in the narrow part is slower Awide/ Anarrow. B) Flow speed in the narrow part is slower widearrow. C Flow speed in the narrow part is faster by a factor Awide/ Anarrow- D) Flow speed in the narrow part is faster by a factor widearrow.Problem 9 (6.25 pts): Three blocks, A, B, and C, are lowered into a tank of water. A and B both have a mass of 40 g; C has a mass of 50 g. All three blocks have the same volume. Rank the readings on the spring scales once the blocks are submerged: 409 50 g 40 g A) A=B=C B) C>B>A C>A=B ) B>A=C E) B>C>A Problem 6 (6.25 pts): A 7 cm-long wind-up fish toy swimming in water has a Reynolds number only a little smaller than a dragonfly in air. What can be concluded from this? Air to dragonflies is like water to the wind-up fish B) Dragonflies fly with the same speed as the wind-up toy swims C) Air has the same density-to-viscosity ratio as water D) Dragonflies move through air with the same ease as large birds move through air