Newton's laws of motion

Newton' first law of motion     

.Every object continues at rest or with uniform velocity unless acted upon by a resultant force.

The inertia of a body is the reluctance of the body to change its state of rest or motion.

Mass is a measure of inertia.

 Newton's second law of motion :   

         F = m a

 Impulse = force X time = change of momentum

                F t = m v – m u

Newton's third law of motion

When two objects interact, they exert equal and opposite forces on one another.

"third-law pair" of forces act on two different bodies.

The principle of Conservation of momentum

For a system of interacting objects, the total momentum remains constant, provided no external resultant force acts on the system.

       total initial momentum = total final momentum

Work, energy and power

       Work done by a force = Force X distance moved along its line of action

 W = F˙Δ d = scalar product of two vectors F and d.= |F| |d| cos a

                                           where a is the angle between F and d.

Work done by a Variable force - One dimensional case

Graphical method : A graph of F against x is plotted.

Work done by the force = area under the curve

Energy is the capacity to do work.

Two types of forces : conservative and nonconservative

Relation between Force and Potential Energy : 

Work-energy theorem :       

Work done by the resultant external force = change of k.e.

Power is the rate of doing work.

        P = F ˙Δ v = |F| |v| cos a        where a is the angle between F and v