Question 4
FrictionWhich of the following statements about friction is NOT correct?
- A.The force of kinetic friction is less than the force of static friction
- B.The force of kinetic friction between two surfaces is independent of the areas in contact provided the normal reaction is unchanged.
- C.The force of rolling friction between two surfaces is less than the force of sliding friction
- D.The angle of friction is the angle between the normal reaction and the force of friction.
- E.Friction may be reduced by lubrication.
Show the answer and explanation
Answer: D (The angle of friction is the angle between the normal reaction and the force of friction.)
Explanation
The normal reaction and friction are always at 90°. The angle of friction is the angle between the normal reaction and the resultant of the normal reaction and friction.