Hello, thank you for the questions!

For ICE 2 #28, to find the height, you need to use some trig. As the passage states, 90 degrees = knee fully flexed, 0 degrees = knee fully extended. In the study, the knee moves from 90 degrees to 30 degrees. To find the change in height, we need to find the length of the side of the triangle when the leg is at 30 degrees. This is one of the special triangle with angles of 30/60/90 with the edges being 1/2/sqrt(3). The edge of the triangle, then, is 0.15 cm. This means that the change in height is 0.3m-0.15m=0.15m. You can now plug this value into W=Fxd to get (500N)x(0.15m) which you can approximate as (500N)x(1/6) to give you the closest answer of D, 75J. Hope this answers your question!

For ICE 2 #45, the question says “meter stick” so the total length of the rod is 1m. With the left side of the rod (relative to the pivot point) being 20 cm, the right side must be 80 cm.

For ICE 3 #48, recall that the RBC has a different mass than the WBC as stated in the passage (RBC=0.5ng, WBC=2ng making the mass of of 1 WBC 4x that of a RBC. My best advice for ratios is setting it up based on what the question is asking (in this case they are asking for the ration of RBC to that of a WBC, or, RBC/WBC) and using the same units. The units I chose to use in my calculation was RBCmass and RBCvol when mass_RBC=1 RBCmass, volume_RBC=1 RBCvol, mass_WBC=4 RBCmass, volume_WBC=2 RBCvol. Hope this helps!