A book is rolled over a few pencils. Choose the most suitable explanation for the force acting between them.
surface of only lower object exerts frictional force on the upper object.
surface of only upper object exerts frictional force on the lower object.
surfaces of both the objects exert force on each other.
surfaces of both the objects exert force in a direction opposite to each other.
Answers
Answer is D.
Explanation:
Friction is a force that resists motion when the surface of one object slides over the surface of another. Frictional forces are always parallel to the surfaces in contact, and they oppose any motion or attempted motion. No movement will occur unless a force equal to or greater than the frictional force is applied to the body or bodies that can move.
The surface of a given material may feel smooth. But at the atomic level, it is filled with valleys and hills a hundred or more atoms or molecules high. When one object is placed on top of another object, the pressure it exerts squeezes the hills and valleys in the two surfaces together. Molecules on the two surfaces tend to stick to one another, producing friction.
Hence, When one object moves over the surface of other object surface of both the objects exert force in a direction opposite to each other.