A block of mass M is placed on a flat surface. A force is applied to move it parallel to the surface. The frictional force f developed is proportional to the :

mass of the body

• The frictional force is a contact force that resists sliding between the surfaces.
• It is denoted as f.
• The frictional force is given by the formula,
• F = μ×N; where μ is the coefficient of friction and N is the normal force.
• The normal force is defined as the support force exerted upon an object that is in contact with another stable object or surface.
• The normal force can be simply described by the following formula: N = mg; where m is the mass of the object and g is the acceleration due to gravity.
• ∴ F = μ × mg
• ⇒ F ∝ m