Non-uniform motion

Need to know

What you need to know

• Momentum is a vector quantity, meaning it has both magnitude and direction.
• Mass is a measure of an object's inertia – its resistance to changes in motion.
• Newton's Second Law can be rephrased: resultant force equals the rate of change of momentum ($F = \frac{\Delta p}{\Delta t}$). This is the most general form of the law, as it applies even when mass is changing (e.g., a rocket burning fuel), whereas $F=ma$ assumes constant mass.
• This definition is particularly useful when mass isn't constant or in impulse calculations.

Explanation

Non-uniform motion

1. Momentum is a vector quantity, meaning it has both magnitude and direction.
2. Mass is a measure of an object's inertia – its resistance to changes in motion.
3. Newton's Second Law can be rephrased: resultant force equals the rate of change of momentum ($F = \frac{\Delta p}{\Delta t}$). This is the most general form of the law, as it applies even when mass is changing (e.g., a rocket burning fuel), whereas $F=ma$ assumes constant mass.
4. This definition is particularly useful when mass isn't constant or in impulse calculations.