A physics explainer video actually explains when it shows the mechanism behind a law, not just the law. Build it in four layers: the everyday observation, what is happening at the level you cannot see (particles, fields, forces), the equation as a summary of that mechanism, and one calculation with real numbers that the viewer could repeat. Then name the misconception your topic is famous for and correct it on screen. Keep it to one phenomenon in three to four minutes, about 450 to 600 spoken words. Draw the hidden level, because that is the part a camera cannot film, and check every arrow, unit and power of ten before you hand it in.

Why most physics project videos do not explain

Watch a stack of student physics videos and the same pattern appears. A title, a definition read from the textbook, the equation, a stock clip of something hot or fast, and a closing line about how physics is everywhere. Everything said is true, and the viewer understands nothing new.

The missing piece is almost always the middle layer: the reason the equation has the shape it does. "Things expand when heated" is a description. "The particles vibrate harder, so on average they sit further apart" is an explanation. A marker can tell the difference in a few seconds, and so can a classmate.

The four layers

Then add one more scene after the calculation: the misconception. Every physics topic has one. Heavy things fall faster. Current gets used up in a bulb. Astronauts float because there is no gravity in orbit. Atoms get bigger when heated. Naming it shows the marker you know where understanding usually breaks.

Worked example: why the Eiffel Tower grows in summer

A good physics project topic has a surprising observation, a mechanism students half know, and a calculation that comes out to a number people can picture. Thermal expansion of the Eiffel Tower has all three.

The facts to check first. The tower is built from puddled iron, a type of wrought iron. Its iron structure is about 300 m tall, with antennas on top bringing it to about 330 m today. The figure usually quoted is that it grows by about 12 to 15 cm on a hot summer day compared with a cold winter one. Because the sun heats one side more than the others, the top also leans slightly away from the sun during the day, by a few centimetres.

The calculation. Linear expansion follows ΔL = α L ΔT.

• α, the coefficient of linear expansion of iron, is about 12 × 10⁻⁶ per °C. That means each metre of iron grows by 12 millionths of a metre for every degree.
• L is the original length: take the 300 m of iron structure.
• ΔT is the temperature change. Paris winters can drop below 0 °C and sunlit iron in summer can pass 35 °C, so take 40 °C as a round, realistic swing.

ΔL = 12 × 10⁻⁶ × 300 × 40 = 0.144 m, or about 14 cm.

That lands inside the quoted range, which is the point of doing it. The calculation is not decoration. It is the evidence that the mechanism you described is big enough to explain what is observed.

The scene list. About 520 words of narration, three and a half minutes.

1. Observation. "On a hot summer day the Eiffel Tower is around fifteen centimetres taller than on a cold winter morning. Nobody adds anything to it." On screen: the tower drawn twice, winter and summer, with the gap at the top marked.
2. Zoom in. "Go down into the iron itself. It is a lattice of atoms, held in place by bonds that act a little like springs." On screen: a grid of atoms joined by springs.
3. The mechanism. "Heat it, and every atom vibrates harder. Because of the way the bonds pull and push, a harder vibration means the atoms sit slightly further apart on average." On screen: the same lattice, atoms with wider vibration marks, spacing slightly larger.
4. The misconception. "The atoms themselves do not get bigger. Each one is the same size. It is the average gap between them that grows." On screen: one atom shown at both temperatures, identical, with the gap highlighted instead.
5. Add it up. "That tiny extra gap, repeated across millions of atoms stacked three hundred metres high, becomes something you could measure with a ruler." On screen: the lattice zooming out into a column, then the tower.
6. The equation. "Physicists write this as delta L equals alpha times L times delta T. Alpha is how much one metre of the material grows per degree." On screen: ΔL = α L ΔT, each symbol labelled with its unit.
7. The calculation. "For iron, alpha is about twelve millionths per degree. Three hundred metres, forty degrees of change. That gives about fourteen centimetres." On screen: the substitution line by line, ending at 0.144 m.
8. The lean. "The sun only ever heats one side, so that side grows a little more, and the top tips away from the sun by a few centimetres." On screen: the tower, one side shaded, a small arrow at the top.
9. Why it matters. "This is why bridges have expansion joints and railway lines have gaps. Engineers design for the metal they cannot stop moving." On screen: a bridge joint and a rail gap, labelled.

Scene 4 is the one most student videos leave out, and it is the one that answers a common exam question.

Draw the part you cannot film

A camera can show a tower. It cannot show atoms vibrating, a magnetic field, the forces on a ladder leaning against a wall, or the energy changes in a pendulum. In physics, the explanation lives in exactly the things you cannot photograph, so a drawn video has an advantage over filmed footage here.

A few rules for those drawings:

• Exaggerate deliberately, and say so. Real atomic spacing changes by a fraction of a percent. Draw it bigger, and have the narration say "exaggerated here so you can see it".
• Arrows carry meaning. A force arrow's direction and relative length are physics. Check both against your free body diagram.
• Units on everything. A number on screen without a unit is wrong in a physics class.
• Keep the same object. If the lattice is iron atoms in scene 2, it is the same lattice in scene 4. Changing the drawing makes the viewer think the thing changed.

Generated drawings are often right about the general shape and wrong about these details: an arrow pointing the wrong way, 10⁻⁶ drawn as 10⁶, a label on the wrong part. Pause on every scene and compare it with your own working.

Topics that work the same way

Each row has an observation people recognise, a mechanism they half know, and a number that makes it real.

Make it

1. 1

   Pick one phenomenon, not a chapter

   Thermal expansion of a real structure, not 'heat'. One observation the viewer has seen or can picture.

2. 2

   Check the facts and do the calculation yourself

   Find the real values, keep units on every line, and make sure your answer is close to the observed figure. If it is not, find out why before writing anything else.

3. 3

   Write the script in layers

   Observation, mechanism, equation, calculation, misconception, why it matters. One idea per paragraph, 450 to 600 words.

4. 4

   Paste it into openCanviz and keep your wording

   Set a three to four minute target. Whiteboard style suits physics because the diagram builds as you explain, the way it would in a lesson.

5. 5

   Check every arrow, unit and power of ten

   Pause on each scene. Fix any wrong label, arrow or number in the editor without regenerating the rest.

6. 6

   Test it on someone who has not studied it

   If they can explain the mechanism back to you in one sentence after watching, the video explains. If they can only repeat the equation, the mechanism scene needs work.

Common questions

How long should a physics project video be? Use the length in the brief. Without one, three to four minutes for one phenomenon. That is long enough for the mechanism and one calculation, and short enough that a viewer keeps the thread.

Should I include a real experiment? If you did one, yes: film it on a phone and use the drawn scenes for the mechanism and the calculation. Real data from your own measurement is worth more marks than a perfect drawing. The two kinds of footage do different jobs.

How do I show an equation without losing the viewer? Show it once, label every symbol with its meaning and unit, and say it in words. Then substitute numbers on the next scene. The same rules for saying maths aloud are in how to make a math explainer video for a class assignment.

Is this different from a general science video? The shapes are the same (process, cycle, comparison, change of scale), covered in how to make a science explainer video for class. Physics adds the calculation, which is where most of the marks sit.

What if my topic is abstract, like fields or energy? Draw what the concept does rather than what it is: a compass needle turning, a ball losing height and gaining speed. How to illustrate abstract ideas has more patterns for this.