In this section of IGCSE Physics, we will be learning about Momentum. While this is a relatively small chapter, here we have laid out the most important concepts that you need to know in order to meet the syllabus requirements for IGCSE Physics.

What is Momentum?

Momentum is the quantity of motion of an object. The two units used to measure moment are kg m/s (kilogram meter per second) and N s (newton seconds).

momentum = mass × velocity
p = mv

Conservation of Momentum

When two or more bodies collide with each other, the total momentum of the bodies remains constant, provided that no external forces act.

Imagine a train is moving at 5 m/s, and it collides with a cart at rest; the mass of the train is 10 kg, and the cart's mass is 1 kg.

After the collision, both start moving together in the same direction; what is the velocity of the combined objects now?

Initial momentum = final momentum, momentum will not change.
Initial momentum = (5 × 10) + (0 × 1) = 50 kg m/s
Initial mass = 10 kg

final momentum = initial momentum = 50 kg m/s
final mass = 10 + 1 = 11 kg

final velocity = 50/11 = 4.55 m/s


Impulse is the change in momentum of an object and is calculated by multiplying the force applied to the object by the time period over which the force is applied.

Impulse is also equal to force multiplied by time.

Impulse = force × time

Resultant force

The resultant force is the change in momentum per unit time.

Resultant Force = change in momentum/time taken

F = ∆p / ∆t

Alternative To Practical (ATP)

Here is a section where you can take the theory-based knowledge above to the next level.

Down below is a simulator where you can visualize what momentum looks like for particles. Please refer to this guide on how to use the simulation to make the most out of your learning.

Helpful video on Momentum

Let's further sharpen our understanding of Momentum by looking at a couple examples and concepts visually explained in the video below.

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