Mass in Motion
Momentum
Chapter 8.1
Momentum Objectives (leave
space in between)
1.
2.
3.
4.
What is momentum?
What is the equation for momentum?
How does changing mass and changing
velocity affect momentum?
How can two objects of vastly different
masses have the same momentum?
Momentum Defined
1. What is momentum?

The product of mass (m) times velocity (v)
 Momentum is mass in motion
2. What is the equation for momentum?
p = mv
 p is the symbol used for momentum
 Unit for momentum is kg x m/s

Momentum
3. How does changing mass and changing
velocity affect momentum?
As the mass or speed increases or
decreases, so does the momentum (direct
relationship)

4.
Double the speed or mass, double the
momentum
How can two objects of vastly different masses
have the same momentum?

A small-massed object with a large speed can
have the same momentum as a large-massed
object with a small speed.
8.1 Momentum
A truck rolling down a hill has more momentum than a roller
skate with the same speed. But if the truck is at rest and the
roller skate moves, then the skate has more momentum.
8.1 Momentum
think!
Can you think of a case where a roller skate and a truck
would have the same momentum?
8.1 Momentum
A truck rolling down a hill has more momentum than a roller
skate with the same speed. But if the truck is at rest and the
roller skate moves, then the skate has more momentum.
A small-massed
object with a
large speed can have the same
momentum as a large-massed
object with a small speed.
8.1 Momentum
think!
Can you think of a case where a roller skate and a truck
would have the same momentum?
Answer: The roller skate and truck can have the same
momentum if the speed of the roller skate is much greater
than the speed of the truck. For example, a 1000-kg truck
backing out of a driveway at 0.1 m/s has the same
momentum as a 1-kg skate going 100 m/s. Both have
momentum = 100 kg•m/s.
8.1 Momentum
What two factors affect an object’s
momentum?
8.1 Momentum
Momentum is affected by the
mass of the object and its
velocity (or speed).
Momentum is mass in motion!
How to solve momentum problems


At the end of a race, a sprinter with a mass of 80
kg has a speed of 10 m/s. What is the sprinter’s
momentum?
List knowns and unknowns
p= ?
m = 80 kg
v = 10 m/s



State the equation: p = m x v
Plug in knowns: p = 80 kg x 10 m/s
Solve the problem p = 800 kg x m/s
Calculate the momentum of the
following objects…
A 75 kg speed skater moving forward at
1.6 m/s
 A 135 kg ostrich running north at 16.2 m/s
 A 5.0 kg baby on a train moving eastward
at 72 m/s
 A 48.5 kg passenger on a train stopped on
the tracks

Calculate which has the greater
momentum.
A 0.05 kg marshmallow traveling at 1500
m/s or a 10 kg bowling ball traveling at 4
m/s?
 p = 0.05 kg x 1500 m/s

p= 75 kg x m/s

p = 10 kg x 4 m/s
p = 40 kg x m/s

It’s the marshmallow!
More momentum problems
What is the mass of a cart moving at 3.4
m/s if its momentum is 156 kg x m/s east?
 What is the velocity of a 56 kg canoe that
has a momentum of 936.6 kg x m/s?
