Romeo tosses a pebble at Juliet's window. Before crashing through the window the pebble is moving horizontally, having traveled a horizontal distance x and a vertical distance y. Find the magnitude and direction of the pebble's velocity as it leaves Romeo's hand.
The attempts are pretty much any relevent equations I can find. There's no real math, except I know that the initial Vy is 0. I also figured if the projectile was graphed it would be the right side of the vertex of the parabola. This is why t=VSinA/g. I do not know where to go from here though. I was thinking of using y=VsinA*t-.5g(t)^2. but I really don't know
I don't understand this. How can we figure out what t is. I do understand that y = .5gt^2. Just not the rest of it. Any help here would be appreciated!
The attempts are pretty much any relevent equations I can find. There's no real math, except I know that the initial Vy is 0.
Why do you think the Vy=0 initially? You do know that Vy is zero right before the stone hits the window; what does that tell you about that point of the trajectory?
I got my B.S. in mathematics from a no-name university, thought that engineering would whet my appetite for physics, took a few chemical engineering and materials science courses, and am now in the non-thesis no-research M.S. materials science program at the University of Florida. I have no research experience. This is a problem.
I am going to start a career in physics by first obtaining a master's degree. However, I was just told today that PhD programs would look at an earned M.S. in physics and wonder "Why didn't he get his PhD?" (Because most people get PhD's in physics, not M.S.'s, but then again, most people have SOME qualification in physics, whereas I am presently taking my first physics course at the graduate level since 2003).
1) How the heck do I get research experience right now? (Most research experience short of being in a formal degree program is reserved for undergraduates!)
I am pretty confused about what the heck I should do. (Ultimately, I want to go to a tippity-top school for theoretical condensed matter physics, like University of Illinois-Champaign).
SIDE QUESTION: Also, does anyone know how the Memorial University of Newfoundland, Canada, ranks for condensed matter physics, in comparison to other schools?
An M.S. doesn't look so bad - in fact it looks great if you did a great job on it and a not-so-great job as an undergrad. A lot of students who think they have the chops but not the proof that they can cut it at a tippity-top Ph.D. program do an M.S. at a less prestigious school to obtain that proof. So the answer to question 2 is yes. UIUC isn't going to accept you with only a B.S. math unless you ace the physics GRE and have some pretty solid letters of recommendation regarding your physics preparation (I assume you don't have such, or you'd already be at UIUC, no?)... With the M.S., you might at least get the second look.
Of course, I would think students who plan to "move up" after a masters usually would not want to take the non-thesis route!
As far as getting research experience, why don't you just ask? There are professors at UF, I'm pretty sure. Professors with problems. Problems you can solve by consulting the literature, making astute observations, and eventually contributing new knowledge to the world.
: ) Thanks, Will. I feel reassured of getting my M.S. right now. (Just today, I was told that getting my M.S. was not a good idea! Of course, my mind was like "WTF, mate?")
I guess another question: I took the Physics GRE on just my as-is engineering knowledge, and got a 640. I know my score is permanently kept. Should I take it again, as I plan to?
Well, today I just got a worksheet in Physics lesson about nuclear radiations, stuff like alpha, beta and gamma rays... I pretty much understand most of what it was about until this "Right Hand Palm Rule" came up to me in the paper, apparently, from what I understand, it's something to do with obviously magnetic field and force etc... but, what ARE these electrical and magnetic field? How are they differ? I had researched a bit on the internet, but most of them are too difficult for me to understand. I'm always so lost in understanding a lot of theories behind physics. People say you need to be very good in mathematics to study WITH physics, I can't say I'm very good in mathematics, but I have pleasing results in that subjects, however, for physics, its a hard concept to understand. Thank you for the helps.
Electric forces affect all charges, and pull them with the same force and in the same direction whatever their speeds are.
But magnetic fields only affect moving charges, and they pull them perpendicular to their line of movement.
The strength of the pull is proportional to the speed of the charge (so it's zero when the speed is zero).
That's why the particle tracks you see in pictures are usually curved - they're produced by particles in a magnetic field.
(Why does a magnet attract stationary objects with no charge? Well, it only does it for iron and a few other materials, and it has something to do with the electrons in the iron, which are charged and which are moving!)
Thanks for the reply and I actually got some ideas in, what these two things are about. But, another thing came up to me, how come electromagnetic waves are unaffected by any of the two fields?
Because electromagnetic waves (like the photons which are their "dual personalities") have no charge.
Another question(jeez, don't I have so much questions :S), you mentioned that the electric forces pull charges with the same force, does that mean it has a constant?
No, he's just saying that the electric force doesn't depend on the speeds of the charges, or their directions of motion. It depends only on the amount of charge and on the distance between them.
My class does, but reading textbook sometimes confuses me :( I also don't have the idea on where to start of in studying physics, things just won't get into my mind....
Although the intuition makes sense, I am having trouble determining why the following proposition is correct. The document leaves this as an exercise for the reader... great.
Proposition: Suppose A is a set in a topological space, and dA is the boundary of A. If x is in dA, then x is either an isolated point, or a strict limit point of both A and A closure.
2) x in A is isolated if there is an open set E containing x such that E\{x} does not intersect A. x is sooo lonely, surrounded by strangers... ;)
3) x is a strict limit point of A if there is a sequence {x_n} contained in A\{x} such that x_n -> x.
So far, my reasoning is this. Supposing x is not isolated, lets show that it is a strict limit point of A by constructing a sequence {x_n} in A that converges to x. After this, showing it for A closure will just requiring twiddling a few words.
If the number of open sets containing x were countable, {E1, E2, E3, ...}, then I would put x1 in E1\{x}, x2 in (E1 intersect E2)\{x}, x3 in (E1 intersect E2 intersect E3)\{x}, and so forth.
We know these intersections can't be empty - if Ei and Ej are open and contain x, then (Ei intersect Ej) is also an open set containing x. Since x is not isolated, (Ei intersect Ej) must contain some y in A (distinct from x). Thus for a countable number of open sets, we can construct the proper convergent sequence.
However, this logic will not work if there are an uncountable number of open sets. I might be able to extend my argument if only the basis is countable, but we don't know that. For example, in the real numbers centered at 0, you might start making up your sequence based on a particular countable collection of open sets like {Ball(.51), Ball(.501), Ball(.5001), etc} and never get to any of the "smaller" open sets.