Why do objects slide down inclined planes?

Objects slide down inclined planes due to the force of gravity acting on them, which is resolved into two components.

In more detail, when an object is placed on an inclined plane, the force of gravity acting on it can be split into two components. One component acts perpendicular to the plane, and the other acts parallel to the plane. The component of the force of gravity that acts perpendicular to the plane is what keeps the object in contact with the surface of the plane. This force is balanced by the normal force, which is the force exerted by the surface of the plane on the object.

The other component of the force of gravity, which acts parallel to the plane, is what causes the object to slide down the plane. This force is unbalanced, meaning there is no other force acting in the opposite direction to counteract it. As a result, the object accelerates down the plane. The steeper the incline of the plane, the greater this component of the force of gravity becomes, and the faster the object will slide down the plane.

The friction between the object and the plane can also play a role in the object's motion. If the frictional force is strong enough, it can counteract the component of the force of gravity that is trying to pull the object down the plane, preventing the object from sliding. However, if the frictional force is not strong enough to balance this force, or if there is no friction at all, the object will slide down the plane.

In summary, objects slide down inclined planes because of the component of the force of gravity that acts parallel to the plane. This force is unbalanced, causing the object to accelerate down the plane. The steeper the incline, the greater this force becomes, and the faster the object will slide. Friction can also play a role in this process, either aiding or hindering the object's motion depending on its strength.