Centripetal force

The centripetal force is directed on an object in a circular motion towards the center of the circle. We were given a helpful packet with equations and explanations. On the quiz, I did pretty well. I got all the momentum questions right and on the centripetal part, for acceleration I did 4pi^2/t which it should've been t^2. I guess what sort of confuses me is where the force comes from. Like if you think of a runner on the track, the friction is the centripetal force. Its a little confusing that the friction causes the runner to go inwards, but if you think about it, the runners natural tendency would be to go straight. If you look at the diagram above, the runner would follow the path of inertia, but due to friction it doesnt. But this is still confusing I'll be honest. In the picture above is the force coming from the string or the person?
Im decent with calculations and what not because the equations are given. So if the question is asking for velocity, you plug the known information in one of the given equations, but its understanding the equations, and breaking them apart to figure out where they're derived from is what is difficult for me. I feel like I have a general understanding of centripetal force, but I need to work towards a deeper one.

The flying pig, here is a picture of our work. We were trying to find the force on the string and this involved many different equations such as the pythagoreum theorum and the force equations. We had to find the force on the string, so as you see we drew a force diagram. We decided to find the earth force (mass) and the centripetal force, and then with our vector knowledge, we could use the pythagoreum theorum to find the hypotneuse aka the force on the string.

Reflecting on Reflecting!!!/Momentum test corrections

YIKES! My last blog was in January. I feel like since february is a short month, and we've had a break in between, I've been thrown off my blog schedule. Excuses, excuses. Honestly, I think the reason I haven't been blogging is because I put off blogs when I don't understand something. I know this defeats the purpose of reflecting, because if I don't completely understand something I could easily say "this is hard for me to grasp because..." but for some reason I just put it off. I guess I just like to know what I'm talking about, and also sometimes I just don't know what to say in a blog if i'm not understanding the class material. Basically, my last blog was on energy...so that means I skipped over momentum.

Momentum
Momentum was interesting because I though I understood it...and then the test came and :((((. Honestly, I seriously understood all the problems we've white boarded in class so when I didnt do too hot on the test I was slightly surprised because i understand P=MV. Okay so on that test, I didnt even really attempt the last question because the graph confused me, but now I totally get it and i'm like REALLY.
So the graph is a FORCE vs Time graph, and I didnt process that FORCE MULTIPLIED BY CHANGE IN TIME IS IMPULSE. honestly like duh.
So now the problem is straight forward.
A. Impulse of the rocket engine?
F=20 T=.5
(20)(.5)=10
Need to account for the triangle
10(.5)
Answer: 5kgm/s

B. determine rockets burnout velocity
5=.3v
divide by .3
vf=16.7 m/s

C. Determine acceleration
a=v/t
16.7/.5
a=33.3 m/s/s


ON NUMBER 17 I CONVERTED WRONG. honestly the dumbest reason to lose points for. I ALWASY CONVERT CM TO KM. I think its a habit of mine just to turn everything into kilo, but centimeters goes to meters. I literally messed this up on the centripetal quiz the other day too, same exact mistake.

19. I didn't account for direction, and this is important with momentum. Other than that my work is correct

Ratios are too much to reflect on the blog here because I got basically all those wrong. But I went over these with my table and I am aware of what I did right and what was wrong, and I have notes and everything on that. Overall on this test, the ratios were the only thing I feel like I was weak on, but I think since then my understanding has improved.