Recent content by hendrix7

Sorry, earlier replies in error. Thank you BvU; very helpful.

I don't really have any idea. I know that shorter wavelengths refract more on entry to prism; e.g. ultra-violet refracts more than infra-red, but I don't know why they don't join up again when speeding up on exit from the prism.

Thank you, berkeman, that seems clear to me now. I really appreciate that.

Using P = I2R 2502 x 3 = 187.5kW Now, I'm pretty sure that this is correct but my question is how does V = IR fit in with this? So, I = 250 and R = 3 so V must be 750, but what does this 750 volts represent? A voltage drop between two points on the transmission cable? If so, where are the two...

Thanks, kuruman, that makes sense to me, and thanks to everyone else who replied.

800 - (32 x 9.8) = 32v/0.18 where v = velocity this gives me v = 2.736 m/s The answer given, however, is 800 = 32v/0.18, i.e. v = 4.5 m/s The difference, of course, is the weight of the child. I don't understand why this is not allowed for in the net force acting on the child. Can someone put me...

Thanks, Dave, for replying. I now think I know why I was confused. I've read a little more on this and this is what I found out: Ohm's Law is only V = IR if R is constant, i.e. is not affected by a change in temperature or any other external factors. Ohm's Law only states that, in this case, V...

Thanks for your reply. In an earlier part of the question, it said that the voltage was varied to investigate the effect on the current and gave some readings: 3 V gave a current reading of 0.1 A and 5 V gave a reading of 0.14 A. Would I still be able to use Ohm's Law for this data to find the...

I know that Ohm's Law gives me the answer of 0.25 A but what I don't understand is how is it ok to use Ohm's Law when I know that the lamp doesn't obey the law? I know that as the current is increased through the lamp, the resistance increases due to temperature rise which, I am told, makes it...

This is a very basic beginner question but one which confuses me. We are told that voltage = current x resistance but I've also read that we can have a voltage without current. But, if current = zero, then if V = IR, V must be zero. Can someone explain where am I going wrong?

Thank you so much. I understand now and can now solve as either the lift and woman together or the lift alone (after calculating normal reaction of lift on woman). Much appreciated.

Summary:: What constitutes the 'body' when applying equation of motion? I was solving this problem: 'A woman of mass 60 kg is in a lift of mass 250 kg which is accelerating downwards at 3.2 m-2. Find the tension in the cable of the lift.' when I realized that I'm not sure what constitutes the...

Of course! Thank you so much. How did I miss that?

ddd

That's what I thought but now, after looking at this question and a couple of others that are similar, I'm not so sure. Like I say in my original post, how do I know whether to add or subtract the speeds of separation without some knowledge of directions? I'll get different answers depending on...