You can spot the moment it happens in almost every IB Physics class: someone says “the car’s velocity is 60 km/h,” and the room nods like nothing happened.
But in IB Physics, that one word can quietly change the whole problem. It changes what counts as “zero.” It changes what a negative sign means. It changes whether you should be talking about distance or displacement. And once graphs show up, it changes what the axes are even saying.
If you want calmer mechanics questions, cleaner explanations, and fewer lost method marks, the difference between speed and velocity is one of the best early wins.
The 20-second IB Physics checklist
Before you calculate anything, run this mini checklist:
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Are you asked for speed or velocity?
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Does the question mention a direction (east, upward, forward, bearing)?
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Should you use distance (path length) or displacement (change in position)?
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Can your answer be negative?
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Which graph are you reading: distance-time, displacement-time, or velocity-time?
If you want more mechanics practice in the exact style of exam questions, the A.1 Kinematics Questionbank is built precisely for this.
Speed in IB Physics: the scalar that doesn’t care where you went
In IB Physics, speed is defined as the rate of change of distance with time:
speed = distance / time
Speed is a scalar. That means it has magnitude only. No direction attached.
So a student jogging 400 m around a track in 80 s has an average speed of 5 m/s, even though they end exactly where they started.
Key consequences in IB Physics:
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Speed is never negative.
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Speed cannot tell you if something is moving “backwards” or “east.”
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You can travel a large distance even if your overall change in position is small.
For a clean set of definitions that match examiner language, keep the IB Physics Key Definitions bookmarked.
Velocity in IB Physics: speed with direction (and a bigger personality)
Velocity is the rate of change of displacement with time:
velocity = displacement / time
Velocity is a vector. It has both magnitude and direction, which means it can be positive, negative, or zero depending on your chosen axis.
That single detail is why velocity shows up everywhere in IB Physics mechanics:
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Acceleration is defined using velocity, not speed.
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A change in direction counts as a change in velocity.
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Graphs become about signs and slopes, not just “how fast.”
To connect this directly to the next idea you’ll be tested on, read How Do You Find Acceleration From Velocity and Time? and notice how often the vector thinking is doing the real work.
Why speed vs velocity matters so much in IB Physics exam questions
Most students don’t lose marks because they “don’t know the formula.” They lose marks because they used the right formula on the wrong concept.
Here are the classic IB Physics moments where the difference matters:
Motion graphs
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The gradient of a displacement-time graph is velocity.
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The gradient of a distance-time graph is speed.
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The area under a velocity-time graph gives displacement (which can be negative).
If graphs are your weak spot, RevisionDojo’s Motion (2.1) Notes walk through the language and the common traps.
“Constant speed” is not “constant velocity”
A car moving around a circular track can keep the same speed the whole time, yet its velocity is changing continuously because direction is changing. That’s why circular motion involves acceleration even when “nothing is speeding up.”
This idea also shows up when you study drag and equilibrium: at terminal velocity, the object still moves, but acceleration becomes zero. See What Is Terminal Velocity? for a clear mechanics-based explanation.
Method marks and sign conventions
In IB Physics, the negative sign is not decoration. It’s a statement about direction. Velocity problems often reward students who set a positive direction early and stick to it.
To keep your notation consistent under pressure, practice with the official reference layout in the IB Physics Data Booklet and pair it with the strategy guide IB Physics Formula Sheet & Data Booklet Guide.
Common misconceptions IB Physics students make
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Treating distance and displacement as interchangeable.
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Saying “velocity” when no direction is given.
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Forgetting that velocity can be zero at an instant even if the object moves before and after.
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Assuming constant speed automatically means no acceleration.
If your goal is a 7, this is the kind of precision that adds up. The mindset behind it is captured well in The Quest for a 7 in IB Physics.
Bring it home with RevisionDojo
If you’re preparing for exams, treat speed vs velocity as your early confidence builder in IB Physics. It’s one concept, but it upgrades your graphs, your acceleration explanations, and your method marks.
RevisionDojo helps you lock it in through a full toolkit: exam-style practice in the Questionbank, clear Study Notes, rapid Flashcards, and targeted support through AI Chat when you get stuck on definitions or sign conventions. When you want to check how examiners reward working, the Grading tools and Mock Exams make your habits sharper. And if you’re stretching for a 7, Predicted Papers, the Coursework Library, and dedicated Tutors turn weak spots into routines you can trust.
Keep going with the full set of IB Physics posts and make this kind of clarity your default.