1. 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

2. A. The Net Force on a Body and Newton’s First Law
F1 + F2 + F3 + F4 = 0
F =  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

3. B. Mass, Acceleration and Newton’s Second LawF6
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

4. D. Newton’s Third Law and Action-Reaction PairsF1
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 ’

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

6. 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

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