Question

how to do this problem?

Answer 1

we know,

★same nature charges repel each other. e.g repulsive force .

★ opposite nature charges attract each other .

now,

Fnet on point C = attractve Force acted by (-9C ) charge + repulsive force acted by ( +3C) charge .

in vector form we write ,

Fnet = F1 i - F2i

where F2 is repulsive force
F1 is attractive force.

now,

F1 = K|Q||q|/r²
here ,
r = 10 cm
|Q| = 9C
|q| = 2C

F1 = K × 9 × 2/(10/100)² N
= 9× 10^9 × 18 × 100 N
= 162 × 10¹¹ N



similarly , F2 = K|Q'| |q|/r'²

here , |Q'| = 3 C
|q| = 2C
r = 30 cm

F2 = 9 × 10^9 × 3 ×2 /( 30/100)²
= 6 × 100 × 10^9 N
= 6 × 10¹¹ N

hence,

Fnet = 162 × 10¹¹ i -6 × 10¹¹ i
= 156 × 10¹¹ i N
.hence, 156 × 10¹¹ N force act on point C