Download Momentum

Momentum
 Momentum
is what Newton called the
“quantity of motion” of an object.
Momentum
 The
momentum of an object:
 Depends on the object’s mass.
 Momentum
is directly proportional to
mass.
 Depends
on the object’s velocity.
 Momentum
velocity.
is directly proportional to
Momentum
 All
objects have mass; so if an object
is moving, then it has momentum - it
has its mass in motion.
 The amount of momentum which an
object has is dependent upon two
variables:
how much matter is moving?
how fast the matter is moving?
•
•
•
Momentum: "mass in motion”
Equation: p = m x v
Unit: kg*m/s
Where;
p = momentum
m = Mass
v = Velocity
Momentum (p)
 In
symbols:
 Transcription
Triangle
p = mv
m=?
v=?
p
m v
Momentum
 Momentum
is a vector quantity.
 Common units of momentum: kg m/s
Momentum Questions
2. A car possesses 20,000 units of
momentum. What would be the
car's new momentum if ...
a.) its velocity were doubled p = 40,000 units
b.) its mass were doubled p = 40,000 units
c.) both its velocity and mass were
p = 80,000 units
doubled
Ticket of Understanding
 What
are the variables to calculate the
product of momentum?
 What
is the formula?
Momentum Questions
1. Determine the momentum of a ...
a.) 60 kg halfback moving eastward at 9
m/s. p = 540 kg*m/s, east
b.) 1000 kg car moving northward at 20
m/s. p = 20,000 kg*m/s, north
c.) 40 kg man moving southward at 2
m/s. p = 80 kg*m/s, south
If the boulder and the boy
have the same momentum,
will the boulder 1000 kg.
crush the boy 35 kg.?
EXPLAIN.
Hint, Hint, Hint:
Think about the momentum
formula!
p = mv
Impulse
 The
impulse exerted on an object
depends on:
 The force acting on the object.
 Impulse
 The
is directly proportional to force.
time that the force acts.
 Impulse
is directly proportional to time.
Impulse (I)

In symbols:
I = Ft
I
F t
Impulse = change in momentum
F∆t = ∆p = ∆(mv)
F∆t = mvf - mvi
F∆t = m (vf – vi)
∆= Delta = Change
f = final
i = initial
Impulse
 Impulse
is a vector quantity.
 Common units of impulse: N s
Impulse & Momentum
 The
impulse exerted on an object
equals the object’s change in
momentum.
Impulse & Momentum
 In
symbols:
I = Dp
Conservation of Momentum
 Since
impulse = change in
momentum, If no impulse is exerted
on an object, the momentum of the
object will not change.
Conservation of Momentum
 If
no external forces act on a system,
the total momentum of the system will
not change.
 Such
a system is called an “isolated
system”.
Conservation of Momentum
is conserved in every
isolated system.
 Momentum
Conservation of Momentum
 Another
way to think about it is:
Internal forces can never change the
total momentum of a system.
Conservation of Momentum
 In
practice, for any event in an isolated
system:
 Momentumafter
= Momentumbefore
The End.