The gravity exerted by Planet X is less than the gravity exerted by Planet Y.

*Gravitational force comparison:** Planet X has less gravity than Planet Y. - **Acceleration due to force:** The acceleration of an object is given by \( a = \frac{F}{m} \). With the same force applied, the acceleration will be higher where the gravitational pull is weaker. - **Initial acceleration:** Since Planet X has less gravity, the same force will cause the ball to accelerate more on Planet X than on Planet Y. - **Conclusion:** The ball will initially accelerate more on Planet X. **References:** Physics textbooks on Newton's laws of motion, principles of gravitation, and kinematics.