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1. ### Derivative of a signal: is it right?

When I write A\text{rect}_{\Delta}(f-f_0) I mean it's a rect signal with amplitude A (usually a constant), duration Δ and is centered in f_0. So in this case there are 2 rect signals, one centered in -4W on the left and the other one centered in +4W on the right. Both have a duration of 4W...

Anybody?
3. ### Derivative of a signal: is it right?

Hi everyone! I was trying to solve an old exercise but in a different way. It asks to find the signal x(t) given the graphs of |X(f)| and arg[X(f)]. Please refer to the attachment. My stategy this time is as follows: 1) find D(f) by deriving |X(f)| 2) antitransform D(f) and get d(t) 3)...
4. ### Fourier Transform: given X(f), find x(t)

Regarding the 1st addend, is it correct? where Meanwhile I'll work out the 2nd addend.
5. ### Fourier Transform: given X(f), find x(t)

I thought of breaking the equation in 2 pieces: \underbrace{\mathcal{F}^{-1}[ \frac{1}{16}f e^{j2\pi \frac{1}{144W}f }]}_{\text{1st addend}}+ \underbrace{\mathcal{F}^{-1}[\frac{3}{8}We^{j2\pi\frac{1}{144W}f } ]}_{\text{2nd addend}} I know that \mathcal{F}[\delta(t-t_0) ]=e^{j2\pi t_0 f}...
6. ### Fourier Transform: given X(f), find x(t)

Sorry I'm late in replying, I was little busy. So X(f) should be: X(f)= \left\{ \begin{array}{ll} (\frac{1}{16}f +\frac{3}{8}W)e^{-j(-\frac{2\pi}{144W}f)} &, \text{ for -6W $\leq$ f $\leq$ -2W} \\...
7. ### Fourier Transform: given X(f), find x(t)

So you're saying the Amplitude should be something like: \frac{1}{16}f +\frac{3}{8}W \mbox{, for -6W \leq f \leq -2W} -\frac{1}{16}f +\frac{3}{8}W \mbox{, for 6W \leq f \leq 2W} \right. As for the PHASE, it should be: \phi(f)=-\frac{\pi}{72W}f Which by the way means that at...
8. ### Fourier Transform: given X(f), find x(t)

That's rather generic. Can you give me another hint for the amplitude? I suppose it assumes the form of a slope: \phi(f)= m\cdot f
9. ### Fourier Transform: given X(f), find x(t)

Can someone try and help me? Please :(
10. ### Fourier Transform: given X(f), find x(t)

Did I get the module correct? Please help me with the phase, do I have to write a slope's formula?
11. ### Fourier Transform: given X(f), find x(t)

Hi everyone! I'm not sure if I'm posting this question in the right section. Please don't be mad at me if I'm mistaken. Can you please help me solve this problem? Calculate the value of the signal x(t), given its spectrum (see figure in attachment), at the time t=2/W. Attempted...

13. ### Engineering Circuit analysis: find Network Function

how? Where do I get another set of equations? seems as though the node method isn't needed to solve this problem. Do I have to make some adjustments and re-write these equations? If so, what are those adjustments? \left[ \begin{array}{ c c c } (\frac{1}{R} + sC) & 0 &...
14. ### Engineering Circuit analysis: find Network Function

\left \{ \begin{array}{ll} \frac{2}{3}I_g+\frac{1}{3}I_2 &=E_2 \\ \frac{1}{3}I_g+\frac{2}{3}I_2 &=E_3 \end{array} \right. \left \{ \begin{array}{ll} \frac{2}{3}+\frac{1}{3}I_2 &=E_2 \\ \frac{1}{3}+\frac{2}{3}I_2 &=0 \end{array} \right...
15. ### Engineering Circuit analysis: find Network Function

Please see the pic I've attached. Did I get your suggestion right? I thought that since the current is not flowing in the upper part of the circuit because of the open circuit represented by the capacitor, I could just eliminate it with a big red "X". This means that for t>0 the initial...
16. ### Engineering Circuit analysis: find Network Function

Ok. Z is the inverse matrix of Y: Y= \left[ \begin{array}{cr} 2 & -1 \\ -1 & 2 \end{array} \right] \rightarrow Z=\left[ \begin{array}{cr} \frac{2}{3} & \frac{1}{3} \\ \frac{1}{3} & \frac{2}{3} \end{array} \right] So this would be: [Z][I]=[E] \left[...
17. ### Engineering Circuit analysis: find Network Function

As I said in a previous post... What to do now? How to find their values? Help, I'm stuck!
18. ### Engineering Circuit analysis: find Network Function

I'm not sure whether there are any initial conditions on the capacitor and the inductance. After all Ig=1 for t ≤ 0. This certainly leads to some initial condition: L has i(0^{-})\neq 0 and C has v(0^{-})\neq 0
19. ### Engineering Circuit analysis: find Network Function

\left[ \begin{array}{ c c c } (\frac{1}{R} + sC) & 0 & -(\frac{1}{R} + sC) \\ 0 & 0 & 0\\ -(\frac{1}{R} + sC) & 0 & (\frac{1}{R} + sC +\frac{1}{sL}) \end{array} \right] \left[ \begin{array}{ c } E_1 \\...
20. ### Engineering Circuit analysis: find Network Function

Where am I going wrong?
21. ### Engineering Circuit analysis: find Network Function

ok, let me try out... \left[ \begin{array}{ c c c } (\frac{1}{R} + sC) & 0 & -(\frac{1}{R} + sC) \\ 0 & 0 & 0\\ -(\frac{1}{R} + sC) & 0 & (\frac{1}{R} + sC +\frac{1}{sL}) \end{array} \right] \left[ \begin{array}{ c } E_1 \\ E_2 \\...
22. ### Engineering Circuit analysis: find Network Function

I'll go with node method. I'm attaching a new pic with the nodes I'm planning to consider. Before proceeding, could you pls check it out and tell me if it is a wise choice? By the way there was a mistake in my previous post regarding the ideal transformer's equation: not I_3 but V_3 is equal to...
23. ### Engineering Circuit analysis: find Network Function

Given the following circuit: (see attached file) find the Network Function between I_L, flowing as drawn in picture, AND I_g. I guess all the calculation should lead up to an expression like this one: I_L(s)=F(s) I_g(s), where F(s) is a function in "s" which corresponds to the NETWORK FUNCTION...
24. ### Circuit resolution

Can anyone help me? thanks.
25. ### Circuit resolution

Let me try the second part. I'll refer to the 3rd diagram attached. (2) I again need to know (Va-Vb) in order to find Q(fin). The current flows clock wise but I move counter clock wise because I have to go from A to B. (V_A-V_B) +I(r+R) -f=0 (V_A-V_B)= f-I(r+R). (2.1) In the above...
26. ### Circuit resolution

In the given circuit (1st diagram), the switch T is initially down (creates a connection). At a certain instant, the switch is turned off and for a while the circuit is kept in that state(final situation). Find the ΔQ=Q(fin)-Q(init) on the top plate of the capacitor while passing from the...
27. ### Find B at distance r

problem: A capacitor has circle plates with radius R. the plates are at a distance h. between the plates there is a tension V. Find B, magnetic induction, at a distance r from the symmetry axis of the capacitor. See diagram attached. what I did: I know it has to be studied in two different...
28. ### Find electrostatic force between

Is it correct? Is it wrong?
29. ### Find electrostatic force between

find electrostatic force problem: there's a long straight wire with a λ1 charge. at some distance from it there's a bar charged with a λ2 charge. the bar is not parallel to the straight wire, instead it's inclined with an angle "alpha" between the dotted line, parallel to the wire, passing...
30. ### Finding coulmb's force

Got it. Thank you for all your help.
31. ### Finding coulmb's force

F=\int dF=\int E dq_2=\int_D^{D+a} \frac{\lambda}{2\pi\varepsilon_0x}\sigma b dx is it like this? When you say dq = \sigma dA = \sigma b dx is it like you're dividing the layer into thin vertical, rectangular-shaped strips with height=b, and length=dx?
32. ### Finding coulmb's force

Could it instead be this? (3.1) F=\int dF=\int E dq_2=\int \frac{\lambda}{2\pi\varepsilon_0D}dq_2=\frac{\lambda}{2\pi\varepsilon_0D}q_2= q_2=\sigma(a\cdot b) \longrightarrow \ F=\frac{\lambda}{2\pi\varepsilon_0D} \sigma(a\cdot b)
33. ### Finding coulmb's force

if I'm not mistaken, the Electrical field at a distance D from the long straight wire should be this, (2.1) E=\frac{\lambda}{2\pi\varepsilon_0D} (2.2) Since dF=E\cdot dq_2 \text{ and } dq_2=\sigma , (2.3) F=\int dF=\int E dq_2=\int \frac{\lambda}{2\pi\varepsilon_0D}\sigma ok? but...
34. ### Finding coulmb's force

can anyone help. tell me if it's right or wrong.
35. ### Finding coulmb's force

[SOLVED] finding coulmb's force Problem: A very long straight wire has a uniform linear density charge, λ (every dx, linear unit, has a λ charge). At a distance D, from the wire, there's a rectangular layer with length=a and height=b and a uniform superficial density charge, σ (every dS...
36. ### A floating point Notation Exercise

Sorry I didn't get you. The notation is sign / exponent in Exc.2^{e-1} / mantissa norm. 1 & 2 1bit / e bits / (15-e) bits = Tot. 16 bits example suppose we find out e=6 and we want ot represent +1.0101 * 2^3 (doesn't matter what's its...
37. ### A floating point Notation Exercise

hey, I really REALLY, need a help with this exercise, got an exam day after tomorrow. got an idea: suppose I do the 1 to 4 steps for each of the numbers? In the end I see which one "includes" the other and I choose that one. Let's do it. Let's take r, its Order of magnitude is 4...
38. ### A floating point Notation Exercise

Consider a floating point binary notation with 16 bits. From left to right, it consists of 1bit for the sign (0= "+"), e bits for the exponent represented in Excess~2^{e-1} and the remaining bits for the decimal part of the mantissa, normalized between 1 and 2 (1 \leq m <2). a) Calculate the...
39. ### Rotation and force

ok, thanks a lot for your help !
40. ### Rotation and force

Could you just tell me if the axis x and y are right as I drew them? Did I draw all the forces acting on the object correctly ?
41. ### Rotation and force

Why? I agree with the 1st statement, but I'm still having doubts on the direction of the centrifugal force. Is it parallel to the ground (not the cone's surface) point out? Could you just show it with a picture post? This will clear out all my doubts. Thank you.
42. ### Rotation and force

m (\omega^2R) = N+G where N and G stand for Normal force and Gravity force. omega² ∙R is the centripetal acceleration. How do I fit in the friction force? Is it right? I'm pretty much confused so please give me clear hints.
43. ### Rotation and force

the exercise is a little difficult to explain in words, it would be much easier with a picture. An iron cube is on the inside rough surface ( \mu_s=0.5 ) of a cone which is upside down. this cone rotates around its centre axis with a \omega=constant. between the axis and the surface there's...
44. ### Rotation and force

Homework Statement \omega=constant R=0.2m \theta=30° \mu _s=0.5 between the iron cube and the surface \omega_{max}=? Homework Equations Fx=Fsin(α) or cos(α) Friction=µN The Attempt at a Solution in pink I drew the gravity force and the normal force. Which other force...
45. ### Energy and/or dynamics

yeah, I figured it out. Thank you very much for replying!
46. ### Energy and/or dynamics

Homework Statement An object passes through point P0 in the instant t=0, going up with a velocity v0=3m/s along a tilted rough surface (dynamic friction coefficient µd=0.3) which forms an angle α=30° with the "ground". The length L of the slanted surface is practically endless. Find a)h...
47. ### Physics Dynamic problem

ok, thank you very much!
48. ### Physics Dynamic problem

so you are saying N=mg - F∙sin(30°) is not right?
49. ### Physics Dynamic problem

I spoke to my teacher and I understood my mistake. I was thinking that the reaction force to the surface was ALWAYS only "m∙g". Actually the normal force varies, it's not always "m∙g" or, better, it's not just that. The gravity force balances the normal force AND the F_y=F∙sin30° mg= N+...
50. ### Physics Dynamic problem

This is what I figure out of the forces applied to the object. (see the attachment)