• Momentum:- Momentum of a particle (p) is equal to the mass of the particle (m) times velocity
of the particle (v). So, p = mv
• Newton laws of Motion:-
First Law (Law of Inertia): Everybody continues in its state of rest or of uniform motion in a straight line
unless it is compelled by some external force to change that state.
Second Law: The rate of change of momentum of a body is directly proportional to the impressed force
and takes place in the direction of the force.
So, F= dp/dt
This results force acting a body F is equal to the mass of the body m times acceleration of the body a.
So, F = ma
Third Law:
To Every action there is an equal and opposite reaction.
FAB = - FBA
• Impulse:- Impulse of a force is defined as the change in momentum produced by the force and it
is equal to the product of force and the time for which it acts.
So, J = Ft
= mv – mu
• Apparent weight of a man inside a lift:-
, (a) The lift possesses zero acceleration
(fig-1): W = mg
(b) The lift moving upward with an acceleration a (fig-2):
W = mg + ma
= mg + mg
= 2 mg
(c) The lift moving downward with an acceleration a (fig-3):
W = mg – ma
= mg – mg
=0
• Inertial mass (mi)- It is defined as the ratio between force F to the acceleration a a produced in
the body.
So, mi = F/a
Note: When the velocity of a body is comparable to the velocity of light, inertial mass changes with
velocity in accordance with following formula,
mi = mi0/√(1-v2/c2)
Here mi0 is the rest mass of body, v is the velocity of body and c is the velocity of light.
• Conservation of linear momentum:-
In an isolated system (no external force), the algebraic sum of the momentum of bodies,
along any straight line, remains constant and is not changed due to their mutual action and reaction on
each other.
of the particle (v). So, p = mv
• Newton laws of Motion:-
First Law (Law of Inertia): Everybody continues in its state of rest or of uniform motion in a straight line
unless it is compelled by some external force to change that state.
Second Law: The rate of change of momentum of a body is directly proportional to the impressed force
and takes place in the direction of the force.
So, F= dp/dt
This results force acting a body F is equal to the mass of the body m times acceleration of the body a.
So, F = ma
Third Law:
To Every action there is an equal and opposite reaction.
FAB = - FBA
• Impulse:- Impulse of a force is defined as the change in momentum produced by the force and it
is equal to the product of force and the time for which it acts.
So, J = Ft
= mv – mu
• Apparent weight of a man inside a lift:-
, (a) The lift possesses zero acceleration
(fig-1): W = mg
(b) The lift moving upward with an acceleration a (fig-2):
W = mg + ma
= mg + mg
= 2 mg
(c) The lift moving downward with an acceleration a (fig-3):
W = mg – ma
= mg – mg
=0
• Inertial mass (mi)- It is defined as the ratio between force F to the acceleration a a produced in
the body.
So, mi = F/a
Note: When the velocity of a body is comparable to the velocity of light, inertial mass changes with
velocity in accordance with following formula,
mi = mi0/√(1-v2/c2)
Here mi0 is the rest mass of body, v is the velocity of body and c is the velocity of light.
• Conservation of linear momentum:-
In an isolated system (no external force), the algebraic sum of the momentum of bodies,
along any straight line, remains constant and is not changed due to their mutual action and reaction on
each other.
