The force of friction always acts in a direction opposite to that in which the body tends to move
The force of friction is dependent upon the area of contact
The force of friction depends upon the roughness of the surface
The magnitude of the limiting friction bears a constant ratio to the normal reaction between two surfaces
Answer is Right!
Answer is Wrong!
The correct answer is: B. The force of friction is dependent upon the area of contact.
The other options are all laws of static friction.
- Option A: The force of friction always acts in a direction opposite to that in which the body tends to move. This is because friction is a force that opposes motion.
- Option C: The force of friction depends upon the roughness of the surface. This is because the rougher the surface, the more points of contact there are between the two surfaces, and the greater the force of friction.
- Option D: The magnitude of the limiting friction bears a constant ratio to the normal reaction between two surfaces. This is known as Coulomb’s law of friction.
The force of friction is not dependent upon the area of contact. This is because the force of friction is caused by the interaction of the microscopic asperities on the two surfaces. The area of contact does not affect the number or size of these asperities, and so it does not affect the force of friction.