Associate Safety Professional Practice Exam

The maximum frictional force on a resting body is proportional to what?

1. The weight of the object only

2. The coefficient of kinetic friction

3. The resultant of all forces perpendicular to the surfaces in contact and the coefficient of static friction

4. The area of contact between the two surfaces

The correct answer is: The resultant of all forces perpendicular to the surfaces in contact and the coefficient of static friction

The maximum frictional force that can be exerted on a resting body is proportional to the resultant of all forces that are acting perpendicular to the surfaces in contact, as well as the coefficient of static friction. This is based on the principle that static friction opposes the initiation of motion, and its maximum value can be determined by the normal force acting between the surfaces and the inherent material characteristics represented by the coefficient of static friction. When considering static friction, the normal force accounts for the weight of the object and any additional forces that may contribute to the total force pressing the two surfaces together. The coefficient of static friction is a measure of how much frictional force can be generated relative to this normal force before movement occurs. Thus, the relationship can be expressed with the formula: \[ F_{max} = \mu_s \times N \] where \( F_{max} \) is the maximum static frictional force, \( \mu_s \) is the coefficient of static friction, and \( N \) is the normal force. Other options either refer to aspects that do not fundamentally determine the maximum static frictional force or misinterpret the contributions of these factors. The weight of the object, while it contributes to the normal force, is not the