Terauchi, you LIED to me

I distinctly remember him teaching about uniform circular motion. He described that there were two forces: a centripetal force (a force pointing inward) and a centrifugal force (a force pointing outward supposedly according Newton's Third Law that every action has an equal and opposite reaction). Here is what my textbook says:

Figure 5.30b is incorrect because it includes an extra outward force of magnitude m(v^2/R) to "keep the body out there" or "to keep it in equilibrium". There are three reasons not to include such an outward force, usually called centrifugal force ("centrifugal" means "fleeing from the center"). First, the body does not "stay out there": It is in constant motion around its circular path. Because its velocity is constantly changing in direction, the body accelerates and is not in equilibrium. Second, if there were an additional outward force that balanced the inward force, the net force would be zero and the body would move in a straight line, not a circle. And third, the quantity m(v^2/R) is not a force; it corresponds to the ma side of net force F=ma and does not appear in the sum of F. It's true that when you ride in a car that goes around a circular path, you tend to slide to the outside of the turn as though there was a "centrifugal force". But we saw in Section 4.2 that what really happens is that you tend to keep moving in a straight line, and the outer side of the car "runs into" you as the car turns. In an inertial frame of reference there is no such thing as "centrifugal force". We won't mention this term again, and we strongly advise you to avoid using it as well.


Also, as a side note, I noticed that the ways he taught us to measure parabolic motion of falling bodies, while very simple and creative, does not help here. We use trig, not measurements and drawings, as sad as I am to say. And my professor actually cares if I went up to him and told him I was concerned, he'd make an appointment with me and discuss it with me like I was his equal rather than a student he was paid to teach. And even if I am supposedly "wasting my money" coming here because I "have bad study skills and will only end up wasting money", I will at least have a quality education in a social and communal environment where teachers are kind and willing to talk to students as if they were real people.

I'm half-tempted to bring it up to him next time I see him. See what he says. :/ But then again, he'd only tell me that I'm not studying well enough or something.

I like my professor that supposedly doesn't care about me according to Terauchi but actually does and has stories that make sense and isn't about inflating his ego.

Sorry.

That is all.

~E