Mechanics help!!! (1 Viewer)

[philk_93]

Hey guys can anyone help me with a question from patels book, its from exercise 9c question 4, its a circular motion question

 

[michaeljennings]

Descartes can help you. So far I have found him to be the most helpful with explaining mechanics on this forum

 

[khorne]

How about you post it up.

 

[thoth1]

umm i dont have that book. plz post question if u want answer

 

[philk_93]

A model plane of mass 5kg attached to the end of an inelastic wire of length 20m flies in a horizontal circle of elevation 30 degrees, while the other end of the wire is held fixed. If the life (force) L acts at right angles to the wire an L is twice the weight of the plane, find:

a) The speed of the plane in m/s
b) The tension in the wire in Newtons

 

[Dr No]

A model plane of mass 5kg attached to the end of an inelastic wire of length 20m flies in a horizontal circle of elevation 30 degrees, while the other end of the wire is held fixed. If the life (force) L acts at right angles to the wire an L is twice the weight of the plane, find:

a) The speed of the plane in m/s
b) The tension in the wire in Newtons

that's easy

 

[AAEldar]

This is my solution that I did when we did the exercise, so I didn't just redo it then. Hopefully you can follow along.

 

[Dr No]

doing ranga?

 

[Shadowdude]

that's easy

So easy you can't even do it yourself. lolololol

 

[Dr No]

So easy you can't even do it yourself. lolololol

I can, from unsw physics 1A dipshit. Didn't think of that did ya, not too smart aye advanced maths boy XP

 

[Shadowdude]

I can, from unsw physics 1A dipshit. Didn't think of that did ya, not too smart aye advanced maths boy XP

You can? Well, show us your university inspired solution to this problem.

 

[clementc]

What on earth is the "life force" of the plane?! Sounds quite epic.
I'll try to do it but I'll just assume it's like buoyancy force upwards.
Could you post the answers from the textbook here for us to check if our method's correct? Thank you

 

[AAEldar]

What on earth is the "life force" of the plane?! Sounds quite epic.
I'll try to do it but I'll just assume it's like buoyancy force upwards.
Could you post the answers from the textbook here for us to check if our method's correct? Thank you

a) v=19.6 m/s
b) Tension=71.74 N

 

[clementc]

Hey AAEldar, out of interest how do you determine in which direction the life (lift?) force and tension force act? I assumed that tension and lift? both acted up but in opposite horizontal directions, and everything came out whack with negative signs =\
Which means it's in the other direction but I'd already done the entire question by the time I'd realised nooooooooooo.
So I just had to rig it with absolute signs so I didn't get negative roots LOL
brb will post up

 

[clementc]

Here's what I came up with. It's a bit long and convoluted because you need quite a bit of working to get to the exact value, which I think you should leave the answer as.
Kind of stuffed up the guess of what directions the tension/lift force was in so had all this negative shit.

Hope it kind of makes sense? =]

 

[descartes]

Descartes can help you. So far I have found him to be the most helpful with explaining mechanics on this forum

Too kind

 

[AAEldar]

Descartes' setting out is much neater and follows on better than mine haha. Hopefully you understand now?