Gareth56

Thanks. Now I know why there's no explanation in my particular physics book!

I note from reading my physics book that "experiments show that the direction of the force is always perpendicular to the direction of the current and also perpendicular to the direction of the magnetic field". What the book doesn't go on to say is the reason for the preferred perpendicular direction. Does anyone know why the preferred direction is perpendicular? Thanks

If a photon is massless how can the intense gravity of a black hole have any affect it? Ta

Yes it is but in the book the 'm' is missing from the denominator so I am assuming that there is a typo in the book as without the 'm' being in the denominator the answer cannot be 1 - a/g. If there was a mechanism to display an image of the page from the book then I think it would be easier to show what the problem is.

The question is asking for a ratio of force to a persons weight. The solution in the book states the following:- F(rope) = mg - ma and the weight of person = mg therefore the ratio of F(rope) to their weight = (mg - ma)/g = 1.0 - a/g So my question was how do you get from (mg - ma)/g to 1.0 - a/g

Should it be (mg - ma)/mg = 1 - a/g ? If so then there's a typo in the physics book I'm reading.

(mg - ma)/g = 1 - a/g Reasoning = (g - a)/g (because mg - ma = g - a) = g/g - a/g = 1 - a/g Is that correct?

So to sum up then. When a meteoroid hits the Earth it becomes a meteorite however when an asteroid hits the Earth is remains and asteroid and the suffix 'oid' remains. I suppose who's going to argue with an asteroid!!!

So when we hear of the asteroid that wiped out the dinosaurs that is incorrect and it was in reality a very large meteorite? Likewise whenever we hear of any future asteroid impacts they should be called meteoroid impacts. Uni Today

Why is it that when an meteoroid reaches the Earth it's called a meteorite but when an asteroid reaches the Earth it's still called an asteroid?

Why is the radian used as the measurement of angular quantity in physics rather than the [more common] degree? Thanks

Many thanks for your informative reply, I'll study it carefully. Can I just ask what the 'cents' axis represents? Thanks

I understand that only odd harmonics (1st, 3rd, 5th, 7th etc.) can be formed from a closed-open pipe such as a clarinet. So (from my physics book) why in this graph of harmonics of the waveform of a frequency produced by a clarinet does it show odd & even harmonics?

Without friction would water flow or any liquid like blood through veins and arteries? I'm not including the surface that the water is flowing on just the water molecules. Hope that makes sense.

That's what I was thinking. I was checking whether the saying had any scientific validity but clearly it doesn't. Below is a quote from a newspaper (The Press) from the UK which illustrates the saying nicely. "And Tim Stockdale, of Osbaldwick, said: “The roads are like glass and the paths are absolutely impossible to walk on – it’s a complete nightmare. It’s like an ice rink – it’s completely out of control and I feel very sorry for any elderly people.”

During very cold weather conditions when the pavements become covered in ice and snow the saying "it's like walking on glass" refers to the fact that the surface one is walking on is very slippery. On a similar note one also hears the saying (here in the UK at least) "The roads are like glass" again this refers to them being very slippery due to the icy conditions.

When the temperature is very cold I often hear people say that the pavements are "like glass" meaning that they are very slippery. Does glass and rubber (soles of shoes) make for a slippery situation when it comes to walking? I would have though rubber on glass produces a fair amount of friction.

Thanks. I'll have to advise the BBC of their careless use of the English language

Is the phrase "accelerating the speed" (of something) a contradiction? Thanks

I understand that rubbing a glass rod with silk leave the glass rod with a positive charge and rubbing rubber/PVC rod with fur gives the rod a negative charge. So if you wanted a rubber rod to become positively charged would you rub it with silk? Why do some materials accept electrons better than others as in the case of silk and fur?

Many thanks. 'O' level maths was so long ago

Hi can I just ask how and why [math]m[/math] can become [math]\sqrt{m^2}[/math] ? I've just realised that [math]m[/math] is the same as [math]\sqrt{m^2}[/math] So was it really necessary to simplify [math]m \sqrt{ kT/m }[/math] to [math]\sqrt{mkT}[/math] or could you just have left it as it was?

In a book I have the following step isn't clear to me:- r = m x sqrt(kT/m) ------> r = sqrt(mkT) I just can't see the steps that go from the first equation to the second. Could anyone show me the missing step(s)?

So why does high wind speed cause contra-rotation only of some bands and why is it alternating?

If Jupiter is rotating in just one direction why are there bands of clouds that move in alternating directions i.e one band travels West to East then one underneath that flows East to West and so on? Thanks