Recent content by zell99

I'm working in three dimensions. To get the first part I used the result that the minimum distance between two skew lines= (a-b).(p*q)/|p*q| where || means modulus which comes from the fact that the vector across the minimum distance will be perpendicular to both lines, and using the dot...

Homework Statement One of those annoying questions that should be simple, but that I've forgotten how to do: Two lines are given by the equations r1=a+lp and r2=b+mq. Find the condition for the lines to cross, and find there position of intersection. Homework Equations The Attempt...

Has anyone got any ideas? I should have said theta is very small, so small angle approximations are fine where appropriate. Thanks

Thanks for the reply. I gave up in the end and used the Langrange.

Anyone? please.

Sorry my fault, should have been more accurate with words, (I don't think what I meant was right either). I'm still confused so if someone is able to derive or give me a hint towards the second equation I'd be really grateful. Thanks

Thnaks for the reply. I think what you're missing, and what I can't get the right value for, is that now the tension is no longer perpendicular to the gravitational force, due to the combination of strings, for the bottom mass. This will lead to an extra term but I can't get it to come out...

Homework Statement A double pendulum consists of light, inextensible strings, AB and BC each of length l. It is fixed at one end A and carries two particles, each of mass m, which hang under gravity. The pendulum is constrained to move in a vertical plane. The angle between the vertical and AB...

Homework Statement A man, height h, can see a mirage at angles less than a known angle \theta to the horizontal. The refractive index of air is at ground level is known. Find the refractive index of air at height h. Homework Equations Snell's law: n1 sin(\theta 1)=n2 sin(\theta2) where...

Solved it.

Just to clarify since my use of 'last part' wasn't particularly precise, it's part (c) I'm struggling with. Thank you

Thanks for the reply: I've done parts (a) and (b) already, it's the third part I'm struggling with (I can't quite see how your post relates to this bit). I won't post my solutions for these bits unless thay would be helpful, since they are show that... questions.

Homework Statement I've attactched an image of the question, I hope this is ok, if not let me know and I'll copy it out onto a post, The Attempt at a Solution I've done parts (a) and (b) using the total derivative of f ( http://mathworld.wolfram.com/TotalDerivative.html ) but I can't get...