I need this last answer for my homework, can't figure this one out.

The figure below shows two concentric rings, of radii R and R ' = 2.90R, that lie on the same plane. Point P lies on the central z axis, at distance D = 2.10R from the center of the rings. The smaller ring has uniformly distributed charge +Q. What must be the uniformly distributed charge on the larger ring if the net electric field at point P due to the two rings is to be zero?

answer is [________] x Q

The answer comes from this, but this is using different numbers

I need this last answer for my homework, can't figure this one out.

The figure below shows two concentric rings, of radii R and R ' = 2.90R, that lie on the same plane. Point P lies on the central z axis, at distance D = 2.10R from the center of the rings. The smaller ring has uniformly distributed charge +Q. What must be the uniformly distributed charge on the larger ring if the net electric field at point P due to the two rings is to be zero?

answer is [________] x Q

[[(2.10R)^2 +(2.9R)^2]^(3/2)] / [(2.1R)^2 +R^2)^(3/2)] times Q

If I didn't make any mistakes... did it kinda fast.

I need this last answer for my homework, can't figure this one out.

The figure below shows two concentric rings, of radii R and R ' = 2.90R, that lie on the same plane. Point P lies on the central z axis, at distance D = 2.10R from the center of the rings. The smaller ring has uniformly distributed charge +Q. What must be the uniformly distributed charge on the larger ring if the net electric field at point P due to the two rings is to be zero?

answer is [________] x Q

Possible quick answer would be to use the ratio of R:R'

R/1Q = R'/xQ

I'll go grab one of my old physics books to be sure. Might be forgetting something.

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