A body is projected at t = 0 with a velocity 10 ms⁻¹ at an angle of 60° with the horizontal. The radius of curvature of its trajectory at t = 1s is R. Neglecting air resistance and taking acceleration due to gravity g = 10 ms⁻², the value of R is :

(1) 2.5 m
(3) 2.8 m
(2) 10.3 m
(4) 5.1 m