**Reasons why we can easily move our hand in air but need a karate expert to do the same through a solid block of wood:**

**1. Physical Obstruction:**
When we move our hand in the air, there is no physical obstruction or resistance that hinders our movement. The air molecules provide minimal resistance, allowing our hand to move freely. On the other hand, a solid block of wood presents a physical obstruction that impedes the movement of our hand. The wood is dense and rigid, making it challenging to pass through without proper technique and force.

**2. Material Properties:**
The properties of air and wood greatly differ, affecting our ability to move through them. Air is a gas, and its molecules are loosely packed, allowing easy passage of our hand. On the contrary, wood is a solid material composed of tightly packed molecules, providing structural strength and resistance. The density and hardness of wood make it difficult to pass through without proper skill and technique.

**3. Structural Integrity:**
The structure of a solid block of wood is rigid and cohesive, making it challenging to penetrate. It is designed to withstand external forces and maintain its shape. Our hand, on the other hand, is flexible and composed of multiple joints, allowing easy movement. The structure of our hand is not designed to forcefully break through solid objects like wood without causing damage.

**4. Technique and Skill:**
A karate expert possesses the necessary technique and skill to break through a solid block of wood. It involves applying precise force, using specific striking techniques, and targeting vulnerable points within the wood. Karate experts undergo rigorous training to develop the strength, speed, accuracy, and focus required to break objects such as wood. Without the proper technique and skill, attempting to move through a solid block of wood with our bare hand can result in injury.

**5. Focus and Concentration:**
Breaking through a solid block of wood requires intense focus and concentration. A karate expert is trained to channel their mental and physical energy into a single point of impact, enabling them to break the wood. Without adequate focus and concentration, attempting to move through a solid block of wood can result in the dispersion of force and the inability to break through.

In conclusion, the ability to move our hand easily in the air compared to passing through a solid block of wood is primarily due to physical obstruction, material properties, structural integrity, and the necessary technique and skill possessed by a karate expert.

To move our hands in air is easy because in air the force of attraction between particles is very high so we can move our hands in air and in wood the force of attraction between particles of solid is low so we can't move r hand in solids