4 questions regarding electric field

[realz]

Homework Statement

Questions attached

Homework Equations

K=9X10*9
E=KQ/R*2
vf=vi+at

The Attempt at a Solution

I only have idea on question 14 but it's wrong. For others I don't , I can only do simple one like if all the charge in x axis

Question 14:
qE=ma
qE/m=a = 20
vf=vi+at
=50+20(2)
=90

*I've been told that all of the answers for the questions is A

 

[darkxponent]

for Q9 we can use formulae for Electric Field at centre of a circular arc

E = (kq/r) * r*(sin(alpha))/alpha

where alpha is half the angle of arc. In this case alpha= 45

 

[darkxponent]

and Q10 is same as Q9

 

[darkxponent]

answer of Q12 :A

 

[realz]

for Q9 we can use formulae for Electric Field at centre of a circular arc

E = (kq/r) * r*(sin(alpha))/alpha

where alpha is half the angle of arc. In this case alpha= 45

I don't get it. tried but it gave 3.53

and Q10 is same as Q9

can you upload worksheet

answer of Q12 :A

I can do if the point of charge is in y but now if it's in 2 side x and y, can you show me the way?

what about question 14?

 

[cupid.callin]

Dont just mug up the formula. its easier to find it by simple calculus

consider two element dx at angle θ from central element.
their field's sin components will cancell out and thus only cos will remain.
now just integrate.

 

[darkxponent]

I don't get it. tried but it gave 3.53

can you upload worksheet

i just uploaded it but they removed it because i solved the whole question. We can't provide whole solution as per rules of PF. I just read all the rules. And i am not going to break more rules because i already have received a warning. We can only help you solve it.

You should also read the rules https://www.physicsforums.com/showthread.php?t=414380 as you also new to this website.