Recent content by yevi

Well, anyone?

I need some help with "law of total expectation". Sorry for my English, I don't know the right English expressions. The Problem is: People come (show in) with with Poisson rate of 10 people per hour. There is a 0.2 chance that a person will give money to a beggar sitting in the corner. The...

Thank you both!

What do you mean stops at 1 or at 2?

I have the following question: 2 persons shoot it each other. Person A shoots at Person B, if A misses, B shoots at A and so on. The Game continues until one of them hits the other one. Probability that A hits B is P1 ,and probability that B hits A is P2. I need to find the E[X]. They give...

Thank you

why do you multiply 2*pi*Rsin(theta) by Rdtheta? We need area so we must find the integral from circumference... And what is the logic taking circle 2*pi*Rsin(theta) as element of area? Why can't i just use 4\pi r^{2} as the area of the shell?

Why from 0 to pi/2? Can you explain?

A half spherical shell as seen in the picture. http://img219.imageshack.us/img219/3424/picnw3.th.jpg charged with surface density \sigma(\theta)=\sigma_{0}cos\theta Need to find the Electric field in center of the axis. As I see the direction of the electric field is the Z axis...

Anyone? :)

I still don't understand why I can't use gauss here.

what do you mean closed? The tube is hollow... If I can't use gauss, what should i use?

The answer should be: E=2 \pi k\rho\frac{r^2-a^2}{r}\hat{r} So I did something wrong...

A long tube charge with charged with uniform spatial density \rho. The inner radius of the tube is: a The outer radius of the tube is: b Need to find the electric field in: a<r<b My approach is Gauss: E*S=4 \pi kq The S is the Gaussean Surface it should be 2 \pi r^2 ?? and q should be...

GOT IT. Thanks again.