1. Net Force
 In a system of two interacting bodies, each
experience a force exerted by the other. If the
system consist of more than two interacting
bodies, each bodies experience the effect of more
than one force.
 In summary, isolate one body in the system and
identify all the forces acting on it.
 The system in isolating a body is the FREE BODY
DIAGRAM (FBD).

2. The law of Inertia
 It is the resistance offered by bodies to any changes
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in its state of rest or motion.
It is measured in terms of mass. And mass is
measured in kilograms.
“a body that has greater mass has a greater inertia”
The law of Inertia states that “when a body is at rest
will remain at rest, while a body in motion will
continue moving at constant speed in a straight path
unless acted upon by a net force”
Galileo was the first one who explain the
phenomenon of inertia, but it was Newton who
formulated this into a law.

3. The law of Acceleration
 The second law of motion states that” acceleration is
directly proportional to the net force acting on the
body and inversely proportional to its mass follows
the direction of the net force”
 In deriving the formula:
* When the mass is held constant; acceleration α Fnet
*And acceleration is also inversely proportional to the
mass of a certain object: a α 1/m

4. • Combining the 1st and 2nd equation we get;
acceleration is directly proportional to the net force
and inversely proportional to its mass.
Thus we get the equation:
a α Fnet/mass , a= Fnet/mass
Or we can also derive the formula for force:
Fnet=Mass x Acceleration
Where Fnet is in Newton (N)
Mass is in Kilogram(Kg)
Acceleration is in meter per second(m/s²)

5. Impulse and Momentum
 When two vehicles collide, the force of impact is so
great that it causes damage to the vehicles and can
risk the lives of its passenger.
 Example: we consider a car of mass 1000kg cruising
at a speed of 20 m/s(80 km/hr). If the car collides
with a tree and comes to a sudden stop in 0.1 s , its
deceleration will be calculated thus:
a=change in velocity/ change in time
a= (v2-v1)/(t2-t1)

6.  a= (0- 20m/s)/0.1 s
 a= -200m/s (thus negative sign indicates that the
impact force to the car is opposite its direction of
motion)
 Thus impulse is the change in momentum.
 the second law of motion can also be expressed as:
F=m( ∆velocity/∆ time) eq. 12.4
F∆t=m∆v
eq. 12.5
Since:
∆v= Vf-Vi
F∆t=mVf-mVi
eq. 12.6
the quantity mv is called momentum of a moving
body.

7. p=mv
eq. 12.7
 Momentum is represented by p. It is a vector
quantity, which follows the direction of the
velocity v. Otherwise:
∆p=m∆v
eq. 12.8
using equation 12.8 and 12.4 becomes:
F∆t=∆p
The product F∆t is called impulse.

8. THANK YOU
FOR
LISTENING
HAVE A GOOD DAY!!!!!!!!!!!!!!!!