The force of friction between two bodies is?
parallel to contact surface
The force of Friction: It is the opposing force generated due to the contact between any two surfaces depending on the coefficient of friction between the two surfaces
In case of Option A:
The force of friction depends on the normal force that a body exerts on the other body or surface
The frictional force tries to stop the relative motion between the objects by applying force in the opposite direction.
⇒ The force of friction acts parallel to the contact surface as shown in the figure.
In case of Option B:
The normal force acts perpendicular to the contact surface but not the frictional force.
In case of Option C:
The net The force on the body will be inclined at some angle, but the frictional force will be parallel to the contact surface.
In case of Option D:
The whole concept of friction is about contact between two surfaces, Friction arises due to contact of two surfaces so, option D is wrong.
Hence, the correct answer is option A