* Kinetics is the study of the displacement, velocity and acceleration of a body in motion along with the forces responsible for the motion.
* A force applied by an external agency either accelerates or retards a body.
* The tendency of a body moving with uniform velocity in a straight line to stay in motion with the same uniform velocity, when the net external force is zero, is called inertia.
* Inertia also means resistance to change or resistance to acceleration.
Newton’s First Law of Motion
* Newton’s First law of Motion states: ‘’Every object continues to be in its state of rest or of uniform motion in a straight line unless compelled by some external force to act otherwise.’’
* If the net external force on a body is zero, it acceleration is zero and vice-versa.
* A body accelerates only when a net external force acts on it.
Newton’s Second Law of Motion
* Momentum of a body is defined as the product of its mass, m, and velocity, v, and is denoted by the small latter ‘p’ .
* Newton’s Second Law of Motion State that: ‘’The rate of change of momentum of a body is directly proportional to the applied force and takes place in the direction in which the force acts .’’
* Impulse is a large amount of force acting on an object for a very short duration of time.
Newton’s Third Law of Motion
* Newton’s Third Law of Motion states that: to every action there is always an equal and opposite reaction.
* Forces always occur in pairs.
* Force on a body A by body B is equal and opposite to the force on body B by body A.
Conversation of Momentum and Equilibrium of a practice.
* The Law of Conversation of Momentum states that ‘’The total momentum of an isolated system of interacting particles is conserved’’.
* System refers to a conglomeration of particles or bodies.
* For an isolated system, there are no external forces acting on the system.
* When the net external force acting on a particle is zero, the particle is said to in equilibrium.
Friction
* Common forces in mechanics are:
• Gravitational force
• Contact forces
• Tension in cables
• Tension or compression in springs
Lubrication is used to reduce the friction between the surfaces.
The component of force parallel to the contact surfaces of two bodies is called friction.
The frictional force at the point of impending relative motion is called limiting static
frictional force.
The Laws of Friction are
• fs is independent of area of contact
• fs ∝ N or fs= ụs N
• fk ∝ N or fk =ukN
Circular Motion and Banking
* When an object is in uniform circular motion, the force directed towards the centre is called the centripetal force.
* An object moving along a circular path at uniform speed also requires a centripetal force to keep it moving along the desired circular path.
* For an object moving along a level, curved path: Vmax= \sqrt{us Rg}
For an object moving along a banked path (neglecting friction):
v: Vmax= \sqrt{Rg tanθ }
Solving problem Is Mechanics
The Systematic steps involved in solving a problem in mechanics are:
1. Drawing a free-body diagram
2. Choosing all the forces acting on the body.
3. Considering all the forces acting on the body
4. Resolving the forces in the chosen coordinate systems.
5. Applying Newton’s Laws of Motion and solving all the equations to the find the unknown variables.