Momentum

Chapter 8.1

Mass in Motion

Momentum Objectives (leave space in between)

1. What is momentum?

2. What is the equation for momentum?

3. How does changing mass and changing velocity affect momentum?

4. 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

Momentum3. How does changing mass and changing

velocity affect momentum?As the mass or speed increases or decreases, so does the momentum (direct relationship)

Double the speed or mass, double the momentum

4. 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.

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.

8.1 Momentum

A small-massed object with a large speed can have the same momentum as a large-massed object with a small speed.

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).

8.1 Momentum

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 unknownsp = ?m = 80 kgv = 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/sp= 75 kg x m/s

p = 10 kg x 4 m/sp = 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?