The slab experiences downward-directed friction force from the rollers.
The force that prevents motion between two surfaces that are touching one another is known as friction. Without friction, you wouldn't be able to walk since your feet would just slide across the floor. Friction is an essential component of daily living.
A surface cannot be moved by an item due to static friction. The force that prevents a book from slipping off a desk even when the desk is slightly inclined and that enables you to pick up an object without the need for a hand grip item that eludes your grasp.
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