A projectile is fired from the surface of the earth with a velocity of 5 ms^-1 and angle θ with the horizontal. Another projectile fired from another planet with a velocity of 3 ms^-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 ms^-2) is: (given g = 9.8 ms^-2)