An iron bolt of mass 51.5 g hangs from a string 33.3 cm long. the top end of the string is fixed. without touching it, a magnet attracts the bolt so that it remains stationary, but is displaced horizontally 26.0 cm to the right from the previously vertical line of the string.
(a) find the tension in the string.(b) find the magnetic force on the bolt.

Explanation:

Let magnetic force F acts towards right and the string makes an angle of θ with the vertical in equilibrium .Let T be tension in equilibrium

T cos θ = mg

T sin  θ = F

Dividing

Tan θ  = F / mg

F = mg Tanθ

= 51.5 x 9.8 x 10⁻³ x 26 / 20.8                        Tanθ = 26 / 20.8 )

=   630.875 X 10⁻³ N            

here we know that ball will drop down by total distance 3.2 m

so here we know that

now using kinematics

now in the same time it will cover horizontal distance of 0.75 m

so speed of the ball will be

the amount of current in the coil