Question

The magnitude of a frictional force depends on:
A. The surface area of contact
B. The weight of the object
C. The condition of the surface in contact
D. None

Answer 1

Hint: A body moving on a plane surface will come to rest after some time. This means there is a force opposing the motion of that particular body. We call this force the frictional force. Frictional force opposes the relative motion of two surfaces that are in contact.

Complete answer:
Frictional force can be defined as the force that opposes the relative motion of two surfaces that are in contact. Hence we know that the type of surface matters. The frictional force will be more on rough surfaces and smooth surfaces tend to lack friction. This makes it easier to walk on rough surfaces than smooth surfaces. If we are dragging an object along a floor, it will be easier to drag along the smooth surface than a rough surface. This is because due to the lack of friction you need less energy to drag an object along a smooth surface.
Another factor that affects the magnitude of friction is the force applied perpendicular to the surface through which the object is moving. We know that force is directly proportional to the mass of the object. Hence we can say that the magnitude of frictional force will depend on the weight of the object.

Option (B) and Option (C): The weight of the object and the condition of the surface in contact.

Note:
The frictional force will be acting tangential to the surface of contact. When two objects are in physical contact there will be an adhesive force between the molecules or atoms of the two bodies. This adhesive force is responsible for producing the frictional force. The frictional force between two stationary bodies is called static friction and the frictional force between two bodies that are in motion is called kinetic friction.