1. ### How far would physics have progressed without electricity

How far could the study of physics have advanced without the discovery/invention of electricity and electrical power? Or in other words, what fields and major breakthroughs could not have been achieved without the availability or knowledge of manipulation of electricity?
2. ### Direction of Frictional Force

Thanks a lot! This suggestion seems to work well for me. And the normal reaction force itself? That is always acting perpendicular to the point or area of contact, i.e. perpendicular to the surface?
3. ### Direction of Frictional Force

But that doesn't answer the question of which line it will act along, in a complicated system. I can't just take components because I need to know which force to equate to the coefficient of friction * normal reaction force and I need to know the direction of that force for this to work.
4. ### Direction of Frictional Force

When a body is held or rests in equilibrium in contact with a surface (e.g. a slope, the edge of a block etc.) how do we work out which direction the friction acts in? I'm used to the friction acting parallel to the surface i.e. slope but in one question I have, of a beam resting on the edge of...

When the contact surface between two conductors is increased, (battery and wire) what happens to the voltmeter reading? If cross-sectional area of wire is increased, current increases but what happens to potential difference on the circuit? Contact resistance is what's varying surely... or...
6. ### Terminal velocity of a person

I did some digging around and came up with an estimate of around 120 mph for a human "in random positions". How about we assume this for terminal velocity? Clearly once the human is "at" or "very near" terminal velocity, we can model speed/distance/time very easily by taking the speed as nearly...
7. ### Cubic equation solutions

I'm finding it hard to find the solutions to this cubic equation: 1/2 x^3 - 2.025647693*10^14 x^2 + 8.102590772*10^11 x - 8.102590772*10^8 = 0 I'm looking for the smallest real positive solution but no matter what solver I use I keep getting only one root (the one of order of magnitude...
8. ### Arrhenius equation and rate of change

Thanks, I had indeed made this mistake - the actual differential should be \frac{d(\frac{dk}{dT})}{d(E_A)} = \frac{A}{RT^2} \cdot e^{-\frac{E_A}{RT}} \cdot (1 - \frac{E_A}{RT}) But it seems that my original conclusion still holds true - that EA < RT (incredibly small activation energy) is...
9. ### Terminal velocity of a person

I want to estimate how long it will take a person (I could specify their dimensions and density :P but maybe just take it as 170 cm tall, 80 kg, etc.) to fall a certain height in the gravitational field of the Earth, not neglecting air resistance. I'm looking at heights anywhere from say 30 m...
10. ### Arrhenius equation and rate of change

Oops I made a stupid mistake here. Sorry if this was confusing people. It should be k2/k1 = exp( EA/R * (1/T1 - 1/T2) ) No squared terms.
11. ### Arrhenius equation and rate of change

I wanted to see how the rate of change of rate constant with temperature (dk/dT) changes with activation energy. I tried to do this with differentials: k=A*e-EA/RT so \frac{dk}{dT} = \frac{A E_A \cdot e^{-\frac{E_A}{RT}} } {RT^2} and then \frac{d(\frac{dk}{dT})}{dE_A} = A \cdot...
12. ### Software for graphing

Thanks for the recommendation. It seems to work for most things and there's loads of documentation but I haven't been able to get this online trial to plot my y-scale too? e.g. http://toycompute.net/?p=1 it's fine when I try code " plot x**2 " but, say, " plot x**2+y**2=6 " and it just plots...
13. ### Software for graphing

Does anyone know any cheap (preferably free) software or online tools for plotting reasonably complicated Cartesian graphs? I would like the functionality to 1) be able to select the range of x and y over which to view the graph, 2) be able to plot multiple functions on the same graph and 3)...
14. ### Hardy-Weinberg question

Ah I see. And any mating between two individuals with different genotypes would also have this multiplying factor of 2 in the calculation of its probability?
15. ### Hardy-Weinberg question

It would seem to me that after monohybrid mating, the frequency of the dominant and recessive allele should change? I will donate original frequency (i.e. proportion) by f0 and that after mating by f1. f1(Dom-Dom) = f0(Dom-Dom)2 + 1/2 * f0(Dom-Dom) * f0(Dom-Rec) + 1/4 * f0(Dom-Rec)2 Am I...