Charge is distributed uniformly on the surface of a large flat plate. the electric field 2 cm from the plate is 30 n/c. the electric field 4 cm from the plate is:

The electric field at 4 cm from the plate is will also be 30 N/C because the distance does not affect the intensity of the electric field.

For a surface with uniform charge density:

Where

- charge density

-  vacuum permittivity

From the equation, the distance does not affect the intensity of the electric field.  Thus, the electric field 2 cm or 4 cm away from the plate will be equal.

Therefore, the electric field at 4 cm from the plate is will also be 30 N/C.

Learn more about Gauss law,

link

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the chart show the masses and velocities of two colliding objects that stick together after a collision.

according to the law of conservation of momentum, the momentum of the object after the collision is  

answer

1,500

kg • m/s.