A small point charge carries a charge of +4 x 10-10 C. 7.1 - Calculate the magnitude of the electric field strength at a distance of 30 mm
from the point charge.

7.2- A second point charge of -8 x 10-10 C is placed at position X. Calculate the
magnitude of the force between the charges.

see explanation

step-by-step explanation:

a

(6r + 7) + (13 + 7r) ( remove brackets and collect like terms )

= 6r + 7 + 13 + 7r

= 13r + 20

b

remove brackets and collect like terms

13 - r - 1 + r

= 12 - r

c

remove brackets and collect like terms

= - 8 - r + 2r - 4

= - 12 + r

d

remove brackets and collect like terms

= 7r - - - 6r

[-   - = - - = - ]

= r -