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Newtons law of Motion

Basic concepts of laws of motion

(1) Newton's first law of motion:-
'A body continues to be in state of rest or uniform motion unless it is acted upon by some external force to act otherwise'

(2) Newton's second law of motion:-
'Rate of change of momentum of a body is proportional to the applied force and takes place in the direction of action of force applied'
Mathematically,
F=dp/dt
=ma
where, F=external force applied
p=mv,momentum of the body
a=acceleration
SI unit of force is Newton (N).

(3) Impulse is the product of force and time which is equal to the change in momentum
Impulse=FΔt
p

(4) Newton's third law of motion:-
'To every action there is always an equal and opposite reaction'
FAB=-FBA

(5) According to the law of conservation of linear momentum
Initial momentum = final momentum
m1v1+m2v2=m1v1'+m2v2'

For equilibrium of a body
F1+F2+F3=0

Some points to note
1. An accelerated frame is called non interial frame while am non accelerated frame is called interial frame
2. Newton Ist law are valid in intertial frame only
3 Apparent weight of a body in the lift
Going Upward with acceleration a
W=m(g+a)
Going Down with acceleration a
W=m(g-a)
4.Always draw free body diagram to solve the force related problems