# Urgent:A lot of questions on a variety of topics

1. Jul 29, 2012

### dawn_pingpong

I'm getting a rather annoyed I have typed all these stuff twice already, and both times the page just tells me to sign in (although I'm signed in already).

1. The problem statement, all variables and given/known data
1) a carnival ferris wheel has a 25m radius and completes five turns about its horizontal axis every minute. What is the acceleration of a passenger at his lowest point?

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2. Relevant equations

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7) three polarising plates are stated. The first and third are crossed, the one between has its polarising direction at 45 degrees to the polarising direction of the other two. what fraction of the intensity of an originally unpolarised beam is transmitted by the stack?
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3. The attempt at a solution
1) I use formula a=4(pi*r*f)^2 so I got 60++. However the answer is 4.1m/s^2
2) I know use the formula R=ρl/A, but I don't know how to do if there are 2 materials of different resistivity.
3) apparently we will need to use boyle's law, But I dont know how to use it.
4) I have no idea what the question is about...
5) Can use E=mc^2, to find that it is 8.5kg/s and thus 7.3 x 10^5 kg/day. But then the ans is 1.8*10^5
6) Fleming's Left hand rule does not work. or is it about cross product?
7) I thought that it should be 25%, however the answer is 12.5%. Why?
8) I used P=VI, and V=IR, to find that the resistance of the wire is 120Ω. So when it is halved, apply the 2 equations again, and found that the total power is 480W. However, the ans is 800W.
9) For this question, i considered 2 forces: F(float)=ρVg and gravity. However, I was unable to obtain the answer. Let x= the mass of Hg needs to be added. then 9.81*1/7870+9.81=9.81*(x/13550)+9.81x. solving for x, x=1.000058, which is not the ans obviously.

Any inputs will be appreciated:) These are not homework questions as per say, just some practice question for a comp I'm going for next week. Last minute cramping! My foundation is rather weak, so it will be good if anyone can provide some partial solution (or intuition) to some of the questions! Help greatly appreciated!