Question

ABC is a right angled triangle in which AB = 3 cm and BC = 4 cm. L ABC = `pi/2`. The three charges+ 15, + 12 and -20 e.s.u. are placed respectively on A, B and C. The force acting on B is ______.

Options

• 125 dyne

• 35 dyne

• 25 dyne

• Zero

Answer 1

ABC is a right angled triangle in which AB = 3 cm and BC = 4 cm. L ABC = `pi/2`. The three charges+ 15, + 12 and -20 e.s.u. are placed respectively on A, B and C. The force acting on B is 25 dyne.

Explanation:

Net force on B, `"F"_"net"` = `sqrt("F"_"A"^2 + "F"_"C"^2`

`"F"_"A" = 15 xx 12/(3)^2` = 20 dyne, `"F"_"C"` = `12 xx 20 /(4)^2` = 15 dyne

`=> "F"_"net" = sqrt("F"_"A"^2 + "F"_"C"^2) =  sqrt((20)^2 + (15)^2)` = 25 dyne