1. Identify the Force: The force exerted by the wedge on the block is the Normal Reaction force ($N$), which acts perpendicular to the surface of the wedge.
2. Analyze Motion (Inertial Frame): The block moves horizontally with the same acceleration $a$ as the wedge. It has no vertical acceleration.
3. Resolve Forces:

• Vertical forces: The vertical component of the Normal force ($N \cos\theta$) acts upwards, and gravity ($mg$) acts downwards.
• Since vertical acceleration is zero, these forces must balance: $N \cos\theta = mg$ [Source 125]

4. Solve for N: $N = \frac{mg}{\cos\theta}$

Alternative (Non-Inertial Frame): Using the concept of pseudo force ($ma$) acting opposite to the acceleration [Source 35]. The components perpendicular to the incline balance out: $N = mg \cos\theta + ma \sin\theta$ To prevent slipping, the components along the incline balance: $ma \cos\theta = mg \sin\theta \implies a = g \tan\theta$. Substituting $a$: $N = mg \cos\theta + m(g \tan\theta)\sin\theta = mg(\cos\theta + \sin^2\theta/\cos\theta) = mg/\cos\theta$.