Deck.Toys includes built-in AI tools inside the Slide editor to help teachers turn a slide into questions, vocabulary work,...
Film a Ruler Demonstration with Three Question Stops
Boon Jin
A ruler demonstration needs a clear view of two ends. Here is a 45-second clip you can film on a table: show a measuring mistake, correct it, then check whether students can measure when the object does not start at zero.
Deck.Toys now lets you upload your own videos into Media Library, trim the part you want, and reuse the clip across decks. This example gives you something specific to record and three questions to place on its timeline.
Set up the shot before pressing Record
Use a ruler marked in centimetres, a plain background, and a paper strip exactly 6 cm long. Measure and cut the strip beforehand. Its square ends will be easier to align than a pencil's pointed tip.
Place the phone directly above the table, with the ruler horizontal and the strip parallel to it. Support the phone securely; avoid filming at an angle. Keep the ruler's 0–10 cm marks and both strip ends in the frame. The zero mark may sit slightly inside the ruler's physical edge: students need to see the mark.
Use light from the side so neither your hand nor the phone casts a shadow over the scale. Make a short test recording. If you cannot distinguish the centimetre marks when the video is small, move the camera closer while keeping both ends visible. Film only the materials, with no names on books, faces or classroom lists in the background.
Film the movement, then leave a still frame
These are target times for the finished, trimmed clip. If your movements take longer, choose the equivalent settled frames instead.
| Clip time | What to film | What to say |
|---|---|---|
| 0:00–0:12 | Put the strip's left end at 2 cm and its right end at 8 cm. Withdraw your hand by 0:06 and hold the view. | “The right end is at eight. Does that make the strip eight centimetres long?” |
| 0:12–0:26 | Slide the strip left until its ends align with 0 cm and 6 cm. Finish moving by 0:16; leave both ends unobstructed. | “Let's line the left end up with the zero mark.” |
| 0:26–0:42 | Move the same strip to 3 cm and 9 cm. Withdraw your hand by 0:30 and hold the view again. | “The strip has moved. Has its length changed?” |
| 0:42–0:45 | Keep the final view still. | “Length is the distance between the two ends.” |
Do not put a question halfway through sliding the strip. The useful pause is after your hand has left the frame and students can inspect both endpoints.
Copy these three question stops
Use an MCQ for the first two and a Text response for the explanation. Interactive Video supports Slide apps placed along the timeline.
At 0:09 — spot the setup error
“The strip starts at 2 cm and ends at 8 cm. What must I change to read its length directly from the right-end number?”
- A. Leave the strip where it is and read 8 cm more carefully.
- B. Line the left end up with the 0 cm mark.
- C. Move the right end to the 10 cm mark.
Answer: B. The endpoint reading gives the length directly when the starting point is zero. In this first shot, 8 cm is a position; the strip's length is 8 − 2 = 6 cm.
At 0:22 — read the corrected measurement
“The strip now starts at 0 cm and ends at 6 cm. How long is it? A: 5 cm, B: 6 cm, C: 7 cm.”
Answer: B, 6 cm. Count the six one-centimetre spaces from 0 to 6. Counting both numbered marks as units would give seven; the marks bound the spaces.
At 0:36 — measure without starting at zero
“The same strip now starts at 3 cm and ends at 9 cm. Give its length and explain why it is not 9 cm.”
Expected response: “It is 6 cm long because 9 − 3 = 6. Nine is the reading at the right end, not the distance between the ends.” Counting six centimetre intervals from 3 to 9 is also a valid explanation. If a student writes only “6 cm”, ask how the two ruler readings support it.
Upload the finished recording, give it a recognisable title such as Ruler demo — zero and shifted start, and trim any setup footage before placing the stops. Keep this plain demonstration in Media Library for reuse; the questions can change when the same clip serves a different lesson.
