friction
Sliding large books requires more force than sliding small books because larger books have more mass and surface area, leading to increased friction with the surface they are sliding on. This increased friction makes it harder to overcome the resistance and slide the large books.
This question is ambiguous. It depends on what force you are comparing the friction force with. Friction, itself, is a force, which will be directed in a direction OPPOSITE the sliding or attempted sliding of two surfaces.
gravity
Sliding is made difficult by friction because rough surfaces "grab" whatever is attempting to slide. Sledding is easy because snow eases friction.
gravity
Gravity? the strength of the floor?
Friction is the force that makes it difficult to push an object along many surfaces.
no
It's the mystical force known as "little slow-speed electric motor below the floor of the cooking chamber".
The force of gavity on car exerts friction on the wheels and axle that eventually stop the car from exerting forward force.
Gravity. It's the same force which pulls things down even without water.
First, the pen rolling would be kinetic energy and then the overall process of it falling onto the floor would be gravity.