- #1

arhzz

- 266

- 52

- Homework Statement
- Find the value of the electric charge

- Relevant Equations
- F = q1q2/4pie0r^2

Hello! I am susposed to find the force of q3.The problem is given as in the picture ;

Now we are given a hint,and it says the following:

"First calculate the forces of the individual charges on q3. The superposition principle says that you can then simply add these forces vectorially

to get to the total strength."

Seems pretty straight forward.Now to get the individual forces on q3 I used this formula

$$ F = \frac{q1*q2}{4\pi e0r^2} $$ where e0 is the permatibilty constant and r is the distance between the charges. Now the distance between the charges (q1 to q3 and q2 to q3) I have calculated using Pythagoras theorem.The length of 30 cm and 40 cm should be the cathetus.

So to get the hypotenuse we simply use the formula ## c^2 = \sqrt{a^2+b^2} ## I've also converted the cm to m and the distance should be 0,5m in both cases.

Now I've simply plug this into the formula F. Now ##F_{23} ## and ##F_{13}## should be 0,54N (I can put the calculation in details but I don't think the problem lies here). Now to get the ##F_3## using the hint should be simply adding the forces together.I get a value of ##F_3 = 1,08 N ##. According to the solution sheet this is wrong.The correct solution is 0,862 N. Now I thought okay so maybe I didnt do the hint correctly.So I tried adding them and than getting the length of the vector(that should represent the hypothenuse hence the force.) So if we do that (to get the length you square them both and pull the root). I get 0,76N again not correct. Now I am kind of stumped because this seemed like an relativly easy problem and I am just not getting there.What am I missing?

Thanks!

Now we are given a hint,and it says the following:

"First calculate the forces of the individual charges on q3. The superposition principle says that you can then simply add these forces vectorially

to get to the total strength."

Seems pretty straight forward.Now to get the individual forces on q3 I used this formula

$$ F = \frac{q1*q2}{4\pi e0r^2} $$ where e0 is the permatibilty constant and r is the distance between the charges. Now the distance between the charges (q1 to q3 and q2 to q3) I have calculated using Pythagoras theorem.The length of 30 cm and 40 cm should be the cathetus.

So to get the hypotenuse we simply use the formula ## c^2 = \sqrt{a^2+b^2} ## I've also converted the cm to m and the distance should be 0,5m in both cases.

Now I've simply plug this into the formula F. Now ##F_{23} ## and ##F_{13}## should be 0,54N (I can put the calculation in details but I don't think the problem lies here). Now to get the ##F_3## using the hint should be simply adding the forces together.I get a value of ##F_3 = 1,08 N ##. According to the solution sheet this is wrong.The correct solution is 0,862 N. Now I thought okay so maybe I didnt do the hint correctly.So I tried adding them and than getting the length of the vector(that should represent the hypothenuse hence the force.) So if we do that (to get the length you square them both and pull the root). I get 0,76N again not correct. Now I am kind of stumped because this seemed like an relativly easy problem and I am just not getting there.What am I missing?

Thanks!

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