Hi Fahad,

*For Question 23:*

Why is the answer 0.118 when the answer given in the solution is 1.1?

Also why are litres converted to millilitres when litres are the SI Unit?'

Thanks for catching the typo, I will mention this, it seems the solution should be D.

The litres are converted into cubic metres because we need to cancel the units properly, we have the area of the tube in m^2 and therefore we need to have the volume in m^3 to properly cancel our units and get a velocity in m/s as designated in the answer.

For Question 25:

Is specific gravity always in comparison to water?

Yeah, if I recall canonically specific gravity is defined as the density substance/density standard, where for solids and liquids the standard is pretty much always water for the MCAT (because it has a density of 1 g/mL which is exceedingly convenient).

For Question 36:

Why is there more friction in the middle of a moving fluid in comparison to the edges of a moving fluid? Wouldn't there be more friction at the edges of a moving fluid as they are closer to the edges of the vessel, so they would collide with the vessel more resulting in increased friction?

I'm not 100% sure about this so you might want to ask this in office hours. Friction forces for fluids, or drag forces, aim to slow down fluid flow and are thus higher when a fluid is moving more quickly. Drag forces increase as you move faster (think about having a sunroof open on a car driving down a highway vs driving down a side street slowly). So in comparison to if the fluid was flowing faster near the edges (not in comparison to the fluid in the centre), friction is minimized if the fluid is flowing slower near the edges.

I hope this helps!

Katt