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Kinematics is one of the most important topics in physics and also one of the most misunderstood. Many students try to memorise formulae and definitions without truly understanding what the formulae and definitions really means. But once you grasp the concept of kinematics, it becomes logical, visual, and even fun to do.
In this blog, we’ll break down kinematics step by step, based on essential concepts, distance vs displacement, speed vs velocity, acceleration, and graph interpretation. By the end, you’ll not only understand the theory but also how to think like an A-star Physics student.
Kinematics is the study of how objects move, without considering the forces causing the motion.
In this topic, we focus on,
These form the foundation for many advanced topics in physics. So, mastering it is key.
One of the most common mistakes students make is confusing distance and displacement.
Distance is the total length travelled, regardless of direction.
For example:
If you walk 700 m forward and 300 m back, your total distance is:
700 + 500 = 1200 m
Displacement is the shortest straight-line distance from start to end, including direction.
Using the same example:
So, the displacement is 200 m to the right.
In short, distance tells you how much ground you have covered but displacement tells you where you ended up.
Just like distance and displacement, speed and velocity are often confused.
Speed is the rate of change of distance.
Velocity is the rate of change of displacement.
Let us look at one example to understand the difference. Imagine walking in a circle and ending where you started.
So,
Acceleration is where many students struggle at, but it’s actually very logical.
Acceleration is the rate of change of velocity.
Where,
To help with your understanding, object accelerates when:
There is also positive and negative acceleration.
Let us look at one example to understand this concept:
If a car goes from +12 m/s to –6 m/s:
Graphs are the next most important part to kinematics. Master them and you can solve almost any kinematics question.
1. Distance-Time Graph
A distance-time graph shows how distance changes over time.
So, how we interpret the graph?
2. Displacement-Time Graph
Unlike distance, displacement also includes direction.
When we study the graph, we need to observe the line above or below the axis and its gradient is the velocity.
So, how do we analyse displacement-time graph?
Ask yourself 3 questions:
Description | Graph |
Calculating the gradient of a displacement-time graph will give us the velocity at that point of time. |  |
If the gradient is not constant, instantaneous speed can be calculated by drawing a tangent at that point and calculating the gradient of the tangent. |  |
3. Speed-Time Graph
A speed-time graph shows how speed changes over time.
Key Points
Interpreting Motion
Description | Graph |
Constant gradient |  |
If the gradient is not constant, instantaneous acceleration can be calculated by drawing a tangent at that point and calculating the gradient of the tangent. |  |
Finding Distance using Speed-Time Graph
Distance = area under the graph
For example:
4. Velocity-Time Graph
Velocity-time graphs are more useful because they include direction.
Key Concepts
Important Rule
Description | Graph |
The gradient of a velocity-time graph will give us the acceleration at that point of time. Constant gradient |  |
If the gradient is not constant, instantaneous acceleration can be calculated by drawing a tangent at that point and calculating the gradient of the tangent. |  |
Common misconception
Students often think, “Negative gradient means moving left”
This is wrong!
Correct concept would be,
Kinematics is not about memorising formulas, it’s about understanding motion.
In summary,
If you want to A-star your kinematics, take note of some key points
Kinematics is like learning a new language. It may feel confusing when your first learn it, but once you understand how the pieces fit together, everything becomes intuitive and fun.
And when that happens, physics stops being something you memorise but becomes something you can apply in your daily lives.
All the best for your Physics O Levels! Happy Studying!
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