A uniform bar of square cross-section is lying along a frictionless horizontal surface. A horizontal force is applied to pull it from one of its ends then.

It seems like you didn't provide a specific question related to the scenario you described. However, I can tell you what would generally happen in this situation.

When a horizontal force is applied to one end of a uniform bar of square cross-section lying on a frictionless horizontal surface, the bar will start to move in the direction of the applied force. This is due to Newton's second law of motion, which states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.

Since the surface is frictionless, there is no opposing force to the applied force. Therefore, the bar will continue to move in the direction of the applied force until an external force is applied to stop it.

If you have a specific question about this scenario, please provide more details.