# Recent content by ecoo

1. ### Differential Equation, Rewriting solution

Thanks for the help
2. ### Differential Equation, Rewriting solution

Yes, I have already done the first part. I did do it backwards, however, because I do not know how to solve differential equations (second derivative ---> function) yet.
3. ### Differential Equation, Rewriting solution

Homework Statement (also express C and alpha as functions of A and B) I need help with the second part (rewriting the solution). Homework Equations ejθ = cos(θ) + jsin(θ) The Attempt at a Solution Unfortunately, I can't think of how to even begin solving. I have the notion that I have...
4. ### Momentum Differential Equation

Thank you for the help. I now understand what you were saying before.
5. ### Momentum Differential Equation

I see what you mean, but isn't that taken care of when we have change in time approach 0 (this is my next step to find an expression for change in momentum). And why would that not also apply to the first scenario, where fuel is also leaving while the rocket accelerates?
6. ### Momentum Differential Equation

I set up a differential equation for the change in momentum in a small change in time, according to the diagrams below. The second setup, when I solve, gives the wrong answer.
7. ### Momentum Differential Equation

Homework Statement A rocket sled moves along a horizontal plane, and is retarded by a friction force friction = μW, where μ is constant and W is the weight of the sled. The sled’s initial mass is M, and its rocket engine expels mass at constant rate dM/dt ≡ γ; the expelled mass has constant...
8. ### Reversed limit definition for monotonic functions

I forgot the part where δ > 0 and ε > 0, so I think it would be written like this: ##\forall \, \delta \ > 0, \exists \, \varepsilon(\delta)\ > 0, : \,\vert \, f(x)-L\,\vert \, < \varepsilon(\delta) \Longrightarrow \, 0 < \vert \,x-a\,\vert \,< \delta \,## L is the supposed limit. lim (x ->...
9. ### Reversed limit definition for monotonic functions

Homework Statement Does the delta-epsilon limit definition in reverse work for describing limits in monotonic functions? By reversed, one means for lim (x -> a) f(x) = L if for each δ there corresponds ε such that 0 < | x-a | < δ whenever | f(x) - L | < ε. Homework Equations The Attempt...
10. ### Physics Am I suited to pursue a career in physics?

Why would you want to skip high school? You'll miss the fun parts of being a high school student.
11. ### PF Photo Contest - Eat Your Vegetables! (6/25-7/1)

Holy cow! You put so much oyster sauce... the natural flavor of the vegetable is lost.
12. ### Rearrangement of the letters "mathematics" (probability)

Hey guys, thanks for the help. The answer 1/990 is correct. The reason I got confused was because I focused on, not rearranging the word "mathematics", but the probability of having the first four letters as "MATH". When considering uniqueness as a factor, then the method works. But when...
13. ### Rearrangement of the letters "mathematics" (probability)

Thought about it a bit more... since I used 2*2*2*1 for my combinations of "MATH", then I already assumed that the M's, A's, and T's are unique, so it's all good.
14. ### Rearrangement of the letters "mathematics" (probability)

Homework Statement What is the probability that a random rearrangement of the letters in the word "mathematics" will begin with the latters "math"? Homework Equations Probability = (# of desired results) / (# of total results) The Attempt at a Solution The solution I got was (2*2*2*1) /...
15. ### Are AP Physics 1 FRQ's appropriate for First Year Student

Really surprised with your experiences, Andy, considering what Diaz Lilahk says is very true and normal. Most high school students simply don't care about physics or math, and it makes sense. There are so many other subjects to be interested in. A majority of people will not enter a field that...