A projectile is fired from the surface of the earth with a velocity of 5 m s^$-$1 and angle $\theta $ with the horizontal. Another projectile fired from another planet with a velocity of 3 m s^$-$1 at the same angle follows a trajectory which is identical with the trajectory of the projectile fired from the earth. The value of the acceleration due to gravity on the planet is (in m s^$-$2) is
(Given g = 9.8 m s^$-$2)