ASK YOURSELF!!!!
HOW CAN YOU IDENTIFY NEWTON’S 3RD LAW OF MOTION IN THIS
FAILED WATER ROCKET EXAMPLE???
rd
Newton’s 3 Law of Motion
• Newton’s 3rd Law: every
action has an equal and
opposite reaction.
– When one object exerts a
force on a second object,
the second one exerts a
force on the first that is
equal in size and
opposite in direction.
• Ex. When you jump on a
trampoline, the trampoline
exerts the same force on
you but pushes you the
opposite direction.
Law of Conservation of
Momentum
• Momentum: (p) mass in motion.
p = mv
p = momentum
m = mass
v = velocity
Measured in kg*m/s
Measured in kg
Measured in m/s
– All moving objects
have momentum.
– Momentum is
transferred
between objects in
a collision.
ASK YOURSELF!!!!
HOW CAN YOU IDENTIFY NEWTON’S 3RD LAW OF MOTION IN THIS
BOUNCING PEOPLE’S EXAMPLE??? (Yes, this law comes with a painful
consequence )
Law of Conservation of
Momentum
Example #3: What is the momentum of a car
with a mass of 1300 kg traveling at a speed of
28 m/s?
p=?
m = 1300 kg
v = 28 m/s
p = mv
p = (1300 kg)(28 m/s)
p = 36,400 kg*m/s
Law of Conservation of
Momentum
• In a collision, because the forces acting on
the two objects are equal and opposite
(Newton’s 3rd Law), the transfer of
momentum must be the same.
🡪 Law of Conservation of Momentum:
momentum is never created or destroyed
in a collision, it is only transferred.
Law of Conservation of
Momentum
Example #4: Ball #1 is rolling 11 m/s directly toward a 0.17 kg
ball #2 at rest. During the collision, ball #1 stops and ball #2 is
launched forward at 9 m/s. What is the mass of ball #1? (think
about the Law of Conservation of Momentum)
m1 = ?
v1 = 11 m/s
p1 = ?
m1 = ?
v1 = 11 m/s
p2 = ?
m2 = 0.17 kg
v2 = 9 m/s
m2 =
0.17 kg
p = mv
Due to Law of
conservation of
momentum…
p1 = p 2
v2 = 9 m/s
m1 = p 1
v1
p2 = 1.53 kg*m/s
m1 = 1.53
11
p1 = m1v1
v1
v1
m1 = 0.14 kg
m1 = p 1
v1
p2 = (0.17)(9)