# Impending Motion

When an object is just about to slip from any surface then the state of the object is known as impending motion. When the static friction reaches its maximum limit then the impending motion occurs. The mathematical formula of the impending motion is $$F=\mu _{s}N$$.

Friction will always oppose the direction of slipping at the contacting surface when the object is about to slip from its rest position. To determine this direction, consider how the system would move in the absence of friction with this known as the direction of impending motion.

Impending Motion

## Static Friction

Static friction is the force that causes a body to stay at its resting position. Static force is always a self-operated force hence static friction is always opposite to the applied force. The direction of frictional force is always opposite to the pending motion of bodies. Now if the force exerted increases then the frictional force also increases till $$F<F_{s}$$. Now if $$F=F_{s}$$ then the object will be unstable and will begin to move. There are mainly three areas between static states to moving states and they are impending motion, no motion, and motion.

### Impending Motion, No Motion, and Motion

Impending motion occurs when the object reaches the maximum static friction and the object is about to slip from its static state. The frictional force between the bodies in the case of impending motion is $$F=\mu _{s}N$$. In case of no motion, the body will be in a state where it will not slip and stay at rest. In this case, the object is in an equilibrium state. So in case of no motion, the friction force will be $$F<F_{s}$$. In the case of moving the objects moves in the direction of the applied force. In the case of motion, the frictional force reduces little and it is termed kinetic motion. The frictional force is represented by the term $$F=\mu _{k}N$$. This kinetic force will drop as the velocity increases further.

### Slipping

In a given system resulted from applied forces that create slipping at certain contacting surfaces. Recall that impending motion occurs at a surface where the friction force f and the normal force N are related by $$F=\mu _{s}N$$. Here we will study a different kind of problem where impending motion in frictional systems can result from either slipping or from a pair of interfacing surfaces losing contact with each other. This second situation will be referred to as tipping.

Q.1 Describe impending motion.

Answer: When an object is just about to slip from any surface then the state of the object is known as impending motion. When the static friction reaches its maximum limit then the impending motion occurs.

Q.2: What is kinetic friction?

Answer: In the case of moving the object moves in the direction of the applied force. In the case of motion, the frictional force reduces little and it is termed kinetic motion.

Q.3: Describe maximum static friction.

Answer: Maximum static friction is the upper limit of the frictional force which keeps an object in a rest position. When the object reaches the maximum limit of static friction it starts to move in the direction of applied force.

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