Momentum and Impulse
Momentum(p)-
Momentum and Impulse
Momentum- Newton
referred to it as the
quantity of motion
Momentum and Impulse
Momentum- It is defined
mathematically as the
product of mass and
velocity of an object
Momentum and Impulse
Momentum-
p  mv
Momentum and Impulse
Momentum is a vector
quantity. The
momentum vector
points in the same
direction as the velocity
vector.
Momentum and Impulse
Example – What is the
momentum of a puck
with a mass of 2.0kg
sliding to the right on the
x axis at 2.0m/s
Momentum and Impulse
Example –
m

 m
P  mv   2.0kg   2.0  x  4.0  kg  x
s
s


Momentum and Impulse
The momentum of a
system of objects is
equal to the vector sum
of the momenta of the
individual objects.
Momentum and Impulse
Example –
What is the momentum of a system
consisting of puck with a mass of
2.0kg sliding to the right along the x
axis at 2m/s, and another puck with a
mass of 1.0kg sliding to the left along
the x axis at 5.0m/s
Momentum and Impulse
Example –
P  m1v1  m2 v2 
m
m


  2.0kg   2.0  x  1.0kg   5.0    x  
s
s


 m
 1.0  kg    x 
s

Momentum and Impulse
Impulse (J) is defined as the
change in momentum
J  p f  pi  p
Momentum and Impulse
Impulse (J) is also equal to the average force
acting on an object multiplied by the time
interval during which it is acting.
J  Ft
Momentum and Impulse
Example – a ball with a mass of 0.50kg and
moving with a velocity of 10.0m/s strikes a wall,
and bounces off in the opposite direction at 5.0
m/s. Consider the initial velocity to be positive.
a. Calculate the impulse given to the ball
b. If the contact with the wall lasted for 0.01s
what was the magnitude of the average force
exerted on the ball?
Momentum and Impulse
Example
a.
m
m
kg m

J  p   0.50   v f  vi    0.5kg   5.0  10.0   7.5
s
s
s

Momentum and Impulse
Example
a.
kg m
J  p  7.5
 Ft  F  0.01s 
s
kg m
7.5
s  750 N
F
0.01s
The negative sign indicates that the force acted
in the direction opposing the original motion
Momentum and Impulse
Summary:
momentum
p  mv
impulse
J  p  mv  m  v f  vi   Ft