|
equilibrium so basically
sum all force, 0
forces will be gravity and charge and helium_floating and tension
break tension force on string into 2 parts, horizontal and vertical.
Sooo
Oh the left helium baloon:
4 forces:
1) baloon floating up
2) tension from string pulling down
3) tension from string pulling right
4) electricStatic force pushing right
They sum to 0
On the right balloon
1) same
2) same
3) same but left
4) same but right
They sum to 0
On the mass
1) tension of 2 strings combined, upward
2) Tension of left string going left
3) Tension of right string going right
notice 2,3, cancle
4) Gravity going down
They sum to 0
Unknowns are charge force, helium floating force, rope tension force. 3 unknowns, and you have 3+ equations.
Solve.
|
|
|
Good luck with the test mate, your in physics c? right?
|
I think we've agreed on the correct way to solve the problem.
We just don't know why the solution is wrong.
|
On November 06 2009 13:13 StorrZerg wrote:
Good luck with the test mate, your in physics c? right?
umm, first year second semster physics, it's called "Physics 2: Physical Science & Technology" lol. It's just the standard second semestre physics subject at my uni (otherones are like biological physics and advanced).
edit: re-reading the problem, it says the weight at the bottom "weighs" 5g... not that it's "mass" is 5g... could this be our source of error? (ie, force should be 5*9.8, not 0.005*9.8?)
|
United States24793 Posts
On November 06 2009 13:24 Ftrunkz wrote:
edit: re-reading the problem, it says the weight at the bottom "weighs" 5g... not that it's "mass" is 5g... could this be our source of error? (ie, force should be 5*9.8, not 0.005*9.8?)
Eh, you can try substituting in the new number and see what you get but, that would be an incredibly stupid thing to do...
|
On November 06 2009 13:13 SanguineToss wrote:
evan are u a teacher?
nope but I tutor math, or used to.
|
Yeah, I also get Q = 5.55 * 10^-7 using the below three equations...
arcsin(a) = 30/100
mg = 2Tcos(a)
Tsin(a) = kQQ/r^2
|
They used 60/(100*100) for r^2.
If it wasn't your teacher that made the mistake you might be able to wiggle some bonus out of it.
|
51679 Posts
i'm so happy i dropped physics for my hsc, it's just nothing but maths and theory =[
|
On November 06 2009 15:35 GTR wrote:
i'm so happy i dropped physics for my hsc, it's just nothing but maths and theory =[
Which is what's so wonderful about it!
|
United States24793 Posts
On November 06 2009 15:35 GTR wrote:
i'm so happy i dropped physics for my hsc, it's just nothing but maths and theory =[
This is so wrong!
|
|
|
|
|
|
EPT
