1. **Stating the problem:** A 4 kg block is sliding on a horizontal surface at constant speed with a force $P$ applied at an angle of 30° above the horizontal. We need to determine the direction of the friction force. 2. **Key concept:** When an object slides at constant speed, it means the net force in the direction of motion is zero (Newton's first law). Therefore, friction acts to oppose the motion. 3. **Analyzing the forces:** The applied force $P$ has a horizontal component $P_x = P \cos 30^\circ$ and a vertical component $P_y = P \sin 30^\circ$. 4. **Direction of motion:** Since the block slides along the surface, the motion is horizontal in the direction of the horizontal component of $P$ (to the right). 5. **Friction direction:** Friction always acts opposite to the direction of motion. Since the block moves to the right, friction acts to the left along the surface. **Final answer:** The friction force acts horizontally to the left, opposite the direction of the block's motion.