Correct Answer - C
When the car is moving in a horizontal track of radius `10 m` with constant speed, then the bob is also under going a circular motion. The bob is under the influence of two forces.
i. `T` tension in the rod)
ii. mg( weight of the bob)
Resolving tension, we get
`Tcostheta=mg`.....i
and `T sin theta=(mv^(2))/r`............ii
(Here `Tsintheta` is producing the necessary cenripetal force for the circlar motion)
dividing eqn i and ii we get
`tantheta=(v^(2))/(rg)=(10x10)/(10xx10)=1impliestheta=45^@`