Two charged concentric spheres have radii of 0.008 m and 0.018 m. The charge on the inner sphere is 3.62 10-8 C and that on the outer sphere is 1.62 10-8 C. Find the magnitude of the electric field (in N/C) at 0.012 m.

The electric field is  

Explanation:

From the question we are told that

       The radius of the inner sphere  is  

        The radius of the outer sphere is

       The charge on the inner sphere is  

        The charge on the outer sphere is  

        The position from the  origin is

Generally the electric field is mathematically represented as

The reason for using   for the calculation is due to the fact that the position considered is greater than the but less than

 Here k is the Coulomb constant with value  

    So  

i don't understand. explain it clearly

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.