Electrostatics

1.A small block of mass m is kept a smooth inclined plane of angle 30° between two charged vertical sheet.Electric field E exists between the verticle sides of the walls of the elevator.The charge on the block is +q.Elevator accelerates with acc. a upward. The time taken by block to rech the bottom of incline is??
Ans.2*√2h/[g-qe/m)√3]

2.If Vo be the potential at the orgin in an electric field E =Exi+Eyj,then potential at point P(x,y) is----??

11 Answers

39
Pritish Chakraborty ·

Disclaimer : I am only an amateur in physics.

We have to find the acceleration of the block by force equations.

It is the horizontal direction wrt the block we are concerned with.

qEcos30° + mgsin30° = macos30°

=> 3qE2 + mg2 = 3ma2
=> √3qE + mg = √3ma
=> a = qEm + g3
Now we have the height h from which the block begins from rest, and the acceleration of the block.

h = ut + 0.5at²
=> h = 0 + (qE2m + g2√3) * t²

Looks like my answer's coming wrong..you didn't specify which side the positive plate is on and which side the negative one is..

1
ajoy abcd ·

+ve plate is on the left side...question is from RSM

39
Pritish Chakraborty ·

lol ab khud karo....tabhi qE + mg aa raha hai aur minus nahi :P

1
ajoy abcd ·

Thanks...got it(and sorry for incomplete information)

39
Pritish Chakraborty ·

What about the second one? We somehow have to use V0 but I'm not getting..

1
Manmay kumar Mohanty ·

u know na
E = - dVdr
usng this will help i guess

39
Pritish Chakraborty ·

I did that but not getting...got an integration and I'm getting something like : V = -Exx - Eyy...we have to use V0 too isn't it?

1
ajoy abcd ·

ANS given is V0-xEx-yEy

39
Pritish Chakraborty ·

Yes I'm not getting the V0. Evidently some mistake I've made.

1
ajoy abcd ·

could this be the process????.... .
somebody please confirm...

39
Pritish Chakraborty ·

Yes this is it! We had to take potential difference..lol.
The upper limit is (x, y, 0) btw...but it's alright.
And the lower limit is (0,0,0).

Your Answer

Close [X]