Newton's First Law of Motion (Inertia):
* An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
Applying it to the crate:
* Constant velocity means no acceleration. This means the net force acting on the crate is zero.
* Two forces are acting on the crate:
* Our pushing force (applied force) is in one direction.
* Friction force is in the opposite direction.
* Since the net force is zero, the pushing force and the friction force must be equal in magnitude and opposite in direction.
In simpler terms:
Imagine you're pushing the crate at a steady pace. If the friction force was less than your pushing force, the crate would speed up. If the friction force was greater than your pushing force, the crate would slow down. Because the crate moves at a constant velocity, we know the forces must be balanced.
Important Note: This assumes that the only forces acting on the crate are your pushing force and friction. In reality, there might be other minor forces (like air resistance) that we're neglecting.
