Last December I applied for physics PhD positions in the US. In my personal statements, I mentioned my research interests as well as specific faculty I'd like to work with. What happens if I receive an offer of admission from a school but decide that I'd prefer to do research in a different...
If you simplify 2Pv + (P-2P1)(v) + P(v+u) + P1(v-u), you get 2Pv + (P-2P1)(v) + 2Pv = 5Pv - 2P1v. I could solve for v1, but my answer was independent of u.
Three boats with the same mass P travel in line ahead (one after the other) with the same speed v. Two identical loads of mass P1 each are thrown simultaneously from the middle boat to the front and rear boats with the same speed u relative to the boat. What are the speeds of the boats (v1...
I am a first-year student majoring in physics and (for the time being) philosophy. The courses that I'm taking would also allow me to major in pure maths or applied maths. During my final year at high school, I felt reasonably sure that I wanted to be a physicist. My grades for maths and...
Find the derivative of y = arctan(x^(1/2)).
Using the fact that the derivative of arctanx = 1/(1+x^2) I got:
dy/dx = 1/(1+abs(x)) * (1/2)x^(-1/2)
But my textbook gives it without the absolute value sign. I don't understand why because surely x^(1/2) squared is the absolute value of x...
THANKS. This really helped to clarify many things for me.
My question has now changed to why there is a frictional force on the object on the disc. To make it simpler, I'm reverting back to the book and car example. Say the car accelerates to the left and the book remains in position...
We use free body diagrams quite a lot. I'll give you an example (the one you asked for in post #18).
The free body I had in mind was a small piece of string adjacent to the mass sans the mass. The forces acting on this free body would be the (upwards) tension of the string just above it and...
Okay. That's a bit weird to think about, but if the string is massless, it must be true. If I had to give a formal statement of why what I said is wrong, could I say that NIII is not applicable to massless objects?
I probably need to do some reading about the centrifugal force since this is the first time I'm dealing with it, and I've never heard of "pseudo forces" and don't know what "non-inertial" means. I understand why a centrifugal force is necessary but I don't understand where it comes from (if...
Why does an object on a rotating disc fly off the disc as the speed of rotation is increased?
To accelerate, the object must experience a net force in the direction of acceleration -- in this case, away from the disc, perpendicular to the object's velocity vector. But what is this force...
Another thing.
Does "weightless" mean the sensation that you don't have weight? You must still be experiencing a downwards force (your weight), because you are accelerating downwards with the free-falling lift (although your acceleration relative to the lift is 0). And if you were standing...
Sorry for the late reply, I had some login problems.
Okay, I thought you were still referring to the free-falling string. I understand that bit now.
I know these questions must be really annoying, but I've got one more. Imagine a pulley with a mass exerting a force of 5N on the left end...