One end of a light inextensible string is attached to a block. The string makes an angle of \(\theta^\circ\) with the horizontal. The tension in the string is 20 N. The string pulls the block along a horizontal surface at a constant speed of 1.5 m s\(^{-1}\) for 12 s. The work done by the tension in the string is 50 J. Find \(\theta\).