Explanation: Friction: Friction is an opposing force that comes into play when a body is actually moving (slide or roll) or even tries to move over the surface of another body. Static friction (Fs): It is an opposing force that acts when it tends to move over the surface, but the actual motion is yet not started. Limiting friction: Limiting friction occurs when the moving force and the force opposing motion are equal; any addition to the moving force will cause slipping. Kinetic friction (Fk): kinetic or dynamic friction is an opposing force that is active when a body is actually moving on another surface. Kinetic friction is always slightly less than static friction, Fk s. [ alt="RRB JE ME 60 14Q EMech1 HIndi Diag(Madhu) 10" src="//storage.googleapis.com/tb-img/production/19/07/RRB_JE_ME_60_14Q_EMech1_HIndi_Diag%28Madhu%29%2010.PNG" style=" width: 381px; height: 339px;"> The magnitude of static friction is given as: Fs ≤ μsN where μs = coefficient of static friction, N = normal reaction, and Fs = static friction force. The magnitude of the kinetic friction is given as: Fk = μkN where μk = coefficient of kinetic friction, N = normal reaction, and Fk = Kinematic friction force.