[Challenge] - Evaever's Physics questions

[m@tty]

Are these threads meant to be some kind of challenge? If so, I'll try and leave them for other people and be more discreet if I do answer them.

Where are you getting these questions from, anyway?

[evaever]

they are questions for anyone interested in doing them
you cannot classify them as the challenge kind, they only require the understanding of 11/12 physics
i found them on the internet

[schnappy]

Because g_average is higher maybe? I can't see the graph...

[evaever]

the rope accelerates under 15, 20 N forces

[evaever]

what are the questions marks meant to indicate... order of magnitude???

ohms

ok well i think the answer is just 52 ohms then

between P, Q or X, Y?

[evaever]

From the graph for question 9 in heinemann questions 3.4, if you compare the gravitational potential energy for the 20,000 satellite at 7x10^6m from the earth's centre and 9x10^6, you get:
Ug @ 7x10^6m = mgh = 20,000 x 8 (from graph) x 7 x 10^6 = 1.12 x 10^12
Ug @ 9x10^6m = mgh = 20,000 x 5 (from graph) x 9 x 10^6 = 0.9 x 10^12
From this the gravitational potential energy is higher in the lower orbit, but how can this be right?!?!?!?!

HELP PLEASE!!

you dont use mgh

[evaever]

the reaction force is from?

[Shark 774]

From the graph for question 9 in heinemann questions 3.4, if you compare the gravitational potential energy for the 20,000 satellite at 7x10^6m from the earth's centre and 9x10^6, you get:
Ug @ 7x10^6m = mgh = 20,000 x 8 (from graph) x 7 x 10^6 = 1.12 x 10^12
Ug @ 9x10^6m = mgh = 20,000 x 5 (from graph) x 9 x 10^6 = 0.9 x 10^12
From this the gravitational potential energy is higher in the lower orbit, but how can this be right?!?!?!?!

HELP PLEASE!!

you dont use mgh

So what do you use?

[Shark 774]

I just found out you have to use calculus, therefore vcaa can't ask us a question like this.

[/0]

This is the classic "wheatstone bridge" problem.

The basic rules of VCE physics should allow you to find the resistance between P and Q.

However, there's a little trick with the resistance between X and Y (but if you learn Kirchhoff's laws it's just a standard question). Imagine the 100 ohm resistor and its path simply aren't there, then the route between X and Y becomes a parallel circuit.
Now measure the voltage drops across all resistors. Since 50:125 = 80:200, the voltage drops are in ratio as well. The crucial point is that the potential is the same at P and at Q!

Now add in the 100 ohm resistor, since the potential is same at P and Q, there is no current across it and no voltage across it. You can treat it like it's not there. So to find the total resistance, treat the circuit like a parallel circuit, ignoring the 100 ohm resistor.

[taiga]

Merged all your threads

Keep them all here from now on and if you object to the title, you are able to change it

[m@tty]

Hey you dragged a thread by shark774 in here too - ' "noob" gravitational potential energy problem '

Pick it back out

[schnappy]

I just found out you have to use calculus, therefore vcaa can't ask us a question like this.

You don't have to antidifferentiate, you count the squares/use geometry. They certainly can ask you to do this.

[Mao]

evaever/evaporade/enpassant, whoever you are, listen up.

This is an official warning. I have sufficient grounds to ban all three of your accounts (misleading with multi-account), but seeing as you have made contributions to discussions in various boards, I don't want to ban you.

I appreciate you posting challenge questions to open the minds of these students. I have seen you do the same in maths boards (dating back to 3 years ago actually). This is not the first time I have said this, but I shall re-iterate and spell it out for you. If you already know the bloody answer and the bloody reason, then it's not a genuine question. Stop asking questions with an agenda and posing as if you need help. These questions are all challenge questions, and should be properly tagged as such.

And I emphasize, I do have a bloody problem with this because you are posing as if you need help, that's not the case.

I would like to warn all users of this user (evaever/evaporade/enpassant). This person is not a current student, is extremely intelligent, and is not asking you for help. Everything he/she says is aimed to help you and/or challenge your skills. Do not be misled.

Moderator Action: edited thread title to include '[challenge]' tag

[golden]

From the graph for question 9 in heinemann questions 3.4, if you compare the gravitational potential energy for the 20,000 satellite at 7x10^6m from the earth's centre and 9x10^6, you get:
Ug @ 7x10^6m = mgh = 20,000 x 8 (from graph) x 7 x 10^6 = 1.12 x 10^12
Ug @ 9x10^6m = mgh = 20,000 x 5 (from graph) x 9 x 10^6 = 0.9 x 10^12
From this the gravitational potential energy is higher in the lower orbit, but how can this be right?!?!?!?!

HELP PLEASE!!

you dont use mgh

So what do you use?

Use the graph if one is supplied.