Unit 4.1: Linear Momentum

Introduction

Momentum is a fundamental concept in physics that describes the motion of an object based on its mass and velocity. Momentum is a vector quantity, meaning it has both magnitude and direction.

Key Concepts

Momentum (p): The product of an object's mass and velocity.
Momentum Formula:
p = m ⋅ v
where:
- p = momentum (kg⋅m/s)
- m = mass (kg)
- v = velocity (m/s)
Vector Nature: Because velocity has direction, momentum also has direction.
Conservation of Momentum: In an isolated system, the total momentum before and after an event remains the same.

Tip: Since momentum is a vector, always account for signs (positive or negative) based on direction!

Mathematical Routines

When solving momentum problems, remember:

Momentum Conservation:
p_initial = p_final
Momentum is conserved in all types of collisions, provided no external forces act on the system.
Consider momentum in two dimensions separately for the x and y directions.

Exam Strategy: Identify the system, draw a diagram, and write a momentum equation before solving.

Practice Activities

Activity 1: Calculating Momentum

A 5 kg object moves with a velocity of 3 m/s. What is its momentum?

Activity 2: Comparing Momentum

A 2 kg object moves at 10 m/s, while a 5 kg object moves at 4 m/s. Which has more momentum?

Summary & Exam Preparation Tips

In Unit 4.1, key takeaways include:

Momentum is given by p = m ⋅ v.
Momentum is conserved in isolated systems.
Momentum is a vector and must be treated directionally.

Understanding these concepts will be critical for solving collision and impulse problems in later sections.