Chapter III Dynamics The Net Force on a Body and Newton’s First Law Mass, Acceleration and Newton’s Second lLaw Weight Force of Gravity Newton’s Third Law and Action-Reaction Pairs Force in Circular Motion Frictional Force

A. The Net Force on a Body and Newton’s First Law F1 + F2 + F3 + F4 = 0 F = 0  Fx = 0  Fy = 0 F3 F1 F4 EQUILIBRIUM At rest Moving with constant velocity If the net force exerted on an object is zero, then the acceleration of the object is zero and its velocity remains constant. Inertia An Inertial frame of reference The tendency of an object to resist any attempt to change its velocity is called the inertia of the object. An inertial frame of reference is one that is not accelerating

B. Mass, Acceleration and Newton’s Second Law F6 F5 + F6 + F7 + F8 ≠ 0 F7 F5 F8 Mass is that property of an object that specifies how much inertia the object has. The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. C. Weight/ Force of Gravity W = mg m g W

D. Newton’s Third Law and Action-Reaction Pairs F1 F1 & F2 ; F3 & F4 ; W & W ‘ is Action-Reaction Pairs Equal in Magnitude Apposite in direction Two objects interact (act on different bodies) F2 F3 If you press against a corner of this textbook with your fingertip, the book pushes back and makes a small dent in your skin. If you push harder, the book does the same and the dent in your skin gets a little larger F4 W W ’

E. Force in Circular Motion v as Fs m m = mass v = velocity R = circular radius as = centripetal acceleration Fs = centripetal Force

F. Frictional Force F = f = fs = µs N The Beam nearly move fk = µk N The Beam have moved µs = Coefficient of Static friction µk = Coefficient of Kinetic friction N = Normal force (N) fs = Force of Static friction (N) fk = Force of Kinetic friction (N) Static/kinetic friction coefficient Just depend to rough of surface both of bodies

The values of K and S depend on the nature of the surfaces