# Search results

1. ### Probability math help

1. Homework Statement A new drug is in trial, and it is found that the drug will cause adverse effects on some patient. 5% will have diarrhoea and 3% develop a rash after taking the drug. Also, 7% of patient have either diarrhoea, rash or both after taking the drug. Need to find the...
2. ### Whats the acceleration?

the following data apply to the speaker system: coil diameter = 5.8cm coil turns = 86 coil and cone mass = 30g magnetic flux density = 0.12T Current in the coil = 1.8A Using the above data, the acceleration of the cone will be? A) 12.6 b) 79.3 c) 113 d) 247 This comes from my revision sheet i...
3. ### Experiment and pu tiron nail into water

Re: rusting sorry my computer was having some problems... yes it changes from 2.36 to 2.6 in grams and are both measured in the same condition
4. ### Experiment and pu tiron nail into water

Re: rusting the cathode nail takes 25mins to gain 2.36 -> 2.4. This is not too accurate becuase there are those (green stuff?) form around the nail and when i pull the nail out and measure the weight those green stuff fall out and stay in solution. solution is HCl the rust on cathode...
5. ### Experiment and pu tiron nail into water

Re: rusting well yes when the nail form rust it is heavier but im not sure about the cathode (rusted iron) will gain or lose weight. I re-tested again at school day and still got the same result. So my question is how come the nail rust it gains weight, and when the nail being de-rusted it...
6. ### Experiment and pu tiron nail into water

Re: rusting well the h2o will have impurities, and the nail is actually steel and iron? As part of the experiment i am also to de rust the nail. would the nail suppose the gain weigh after electrolysis? Because when the nail rust it gains weigh, and if de rust will it lose weigh? but my nail...
7. ### Experiment and pu tiron nail into water

So i did an experiment and pu tiron nail into water and serveral days later it starts to rust. and i looked at the book and the chemical process is 1)Fe loses electron 2) that electron + oxygen + water produces hydroxide 3) hydroxide and Fe ion reacts and form Fe(OH)2, green rust 4)...
8. ### How charged particle got to do with magnetism

hello, I am not too sure of how charged particle got to do with magnetism. "Magnetism is a force of attraction or replusion that acts at a distance. It is due to a magnetic field, which is caused by moving electrically charged particles or is inherent in magnetic objects such as a magnet."...
9. ### Find the 50th derivative of the function

Re: [Urgent] Differentiation i know it now... is (-1)^n/2 x a^n cos ax (for even) thx for the help :)
10. ### Find the 50th derivative of the function

Re: [Urgent] Differentiation sorry it should be the 50th derivative
11. ### Find the 50th derivative of the function

1. Homework Statement Find the first, second, third, fourth, fifth derivatives of the function y = sin 3x. Find a rule that can help to find the 50th derivative of the function. It's urgent! 2. Homework Equations y= sin x y= cos x y' = cos x...
12. ### Polar form

1. Homework Statement solve below using de Moivre's theorem, in polar form z^3 = i 2. Homework Equations r CIS theta Answer:CIS pi/6, CIS 5pi/6, CIS (-pi/6) 3. The Attempt at a Solution r^3 = sqrt(0^2+1^2) r^3 = sqrt (1) r = sqrt (1) no idea how to get the angle
13. ### Frequency and penetration depth

ok thx that was very useful!
14. ### Frequency and penetration depth

why does the increase of sound frequency will decrease the penetration depth? how can this related to diffraction of sound?? Is it because they can be easily reflected?? need answer desperately, thx
15. ### Ultrasound machine

hey here is another question :S When the frequency of the wave is too high it will be absorbed easily? I don't understand why. Is it because of the increase in wavelength?
16. ### Ultrasound machine

just wondering, would the change in amplitude (voltage) has any effect on this?
17. ### Ultrasound machine

oops sorry i understand now thx!
18. ### Ultrasound machine

yes it calculates the time that takes to travel back to the transducer to produce an image. but i dont really get this staement below "the crystal will be changed in the same way as when crystal the crystal was generating ultrasound. In this case the changing crystal will cause a changing...
19. ### Ultrasound machine

So when this happens this is the reverse of the piezoelectric effect? (from mechanical energy to electrical energy.) And the transducer receives sound wave because of this reverse piezoelectric effect? also there is the other bit that i dont understand "the crystal will be changed in the same...
20. ### Ultrasound machine

how does ultrasound machine detects the reflected wave? i have read a bit of information and unfortunately Im still unsure how they detect the wave. "The rapid shape changes, or vibrations, of the crystals produce sound waves that travel outward. Conversely, when sound or pressure waves...
21. ### Use the chain rule to find the derivative

Re: Derivative ohh thx! I will try it again (reserved)
22. ### Use the chain rule to find the derivative

1. Homework Statement f(x) = ((x^2+2)^2)/(x+2)^1/2 Use the chain rule to find the derivative 2. Homework Equations None 3. The Attempt at a Solution ((x^2+2)^2)(x+2)^-1/2 PS: Answer in the book is 3x((x^2+2)^1/2) I have no idea how they get it there, would like some help, thx!

:rolleyes:
24. ### Pure carbon and graphite have the same resistivity?

I am just wondering if pure carbon and graphite have the same resistivity? Resistivity for pure carbon = 3.5 x 10^-3Ωm:frown:
25. ### Electrical resistance

and the resisitvity of the material is depending on its own density?
26. ### Electrical resistance

1. Homework Statement this is not a homework question... i want to know density vs resistance 2. Homework Equations R = ρl/a 3. The Attempt at a Solution none so far
27. ### Pascals Triangle

thx for the help :) exams finally over
28. ### Pascals Triangle

independent of x simply means that x^0 and yes I am trying to find the co-efficient there heres are my working out. independent of x in (6x^(2)-3/x)^6 1. (6^(6-r) x^(12-2r) ((-3^(r))/x^(r)) 2. x^(12-2r)/x^(r) = x^(0) 3. x^(12-3r)=x^(0) 4. 12-3r=0 5. r = 4
29. ### Pascals Triangle

how do i find the independent of x in (6x^(2)-3/x)^6 I know that the formula nCr a^(n-r) b^r i have got an answer of n = 6 and r = 4 i just wanna make sure that im correct and i would like someone to give me a hand~ :)
30. ### Spherical coordinate system

(magnitude,angle) The task is to investigate the spherical coordinate system, which I haven't learn but I have no idea what to do