Question

Which of the following statements is not true?
A The coefficient of friction between two surfaces increases as the surface in contact are made rough
B The force of static friction acts in a direction opposite to the applied force
C Rolling friction is greater than sliding friction
D The coefficient of friction between wood and wood is less than 1

Answer 1

Hint: We should know that a force is a push or pull upon an object resulting from the object's interaction with another object. Whenever there is an interaction between two objects, there is a force upon each of the objects. When the interaction ceases, the two objects no longer experience the force.
It should be known to us that balanced forces are those two forces acting in opposite directions on an object, and they are equal in size. Anytime if there is a balanced force on an object, the object stays still or it continues moving at the same speed and in the same direction is called a balanced force.

Complete step by step answer
We know that as the surfaces in contact are made rough, interaction between the surfaces is more established and hence the coefficient of friction between two surfaces increases.
The force of static friction tries to stop the body from moving, so will act in a direction opposite to the applied force (moving will be due to the applied force. Friction always resists relative motion) The coefficient of rolling resistance is generally much smaller than the coefficient of sliding friction.
The coefficient of friction between wood and wood is around $0.25-0.5$ (static) and 0.2(kinetic). Every coefficient of friction is always less than or equal to one. (Only static friction coefficient
in Rubber on Concrete is 1).

Note: It should be known to us that when two forces are the same strength but act in opposite directions, they are called balanced forces. Again, tug-of-war is a perfect example. If the people on each side of the rope are pulling with the same strength, but in the opposite direction, the forces are balanced. The result is no motion. If two individual forces are of equal magnitude and opposite direction, then the forces are said to be balanced. An object is said to be acted upon by an unbalanced force only when there is an individual force that is not being balanced by a force of equal magnitude and in the opposite direction.
According to Newton's Laws of Motion, an unbalanced force is one that causes a change in the motion of the object to which the force is applied. An unbalanced force continues to accelerate an object until a new counterforce builds up and a new balance of forces is established.
We should know that a balanced force only tends to change the shape and size of the body. It does not tend to change the state of motion of the body.