Measurement of Length and Motion · Learner pages

Lesson 1 · Use units that everyone can compare

Choose and convert common length units without changing the measured object.

Name or initials: ____________   Date: ____________

Length tells how far apart two points are. A standard unit makes results comparable. The metre (m) is the SI unit of length.

1. Choose a shared unit. Different people have different hand spans. A result is easier to compare when everyone uses the same agreed unit.
2. Connect metres and centimetres. One metre contains 100 equal centimetres. The same ribbon can be described as 1 m or 100 cm; changing the unit does not change the ribbon.
3. Connect centimetres and millimetres. One centimetre contains 10 equal millimetres. Therefore 1 m contains 1000 mm. Millimetres help describe smaller lengths.
4. Choose a sensible scale. Use millimetres for the thickness of a card, centimetres for a notebook, metres for a room and kilometres for a journey. A measurement always needs a number and a unit.

Worked example: A display ribbon is 2 m 35 cm long. First convert 2 m to 200 cm. Add the remaining 35 cm: 235 cm. Check: 235 cm = 2 m + 35 cm.

1. Which record is a complete length measurement?

   1. 18 · 2. 18 cm · 3. Long

2. A strip is 4 cm long. What is its length in millimetres?

   1. 40 mm · 2. 400 mm · 3. 0.4 mm

3. Why can two learners count different hand spans for the same desk?

   1. The desk must change length · 2. A hand span is always 1 m · 3. Their hand spans may be different sizes

Discuss: Find two labelled lengths at home. Rewrite each in a second suitable unit and explain why both records describe the same length.

Lesson 2 · Measure carefully and check the starting mark

Read a ruler and calculate a length from two endpoints.

Name or initials: ____________   Date: ____________

A ruler measures the interval between two marks. Good alignment and a clear viewing position reduce avoidable reading errors.

1. Place the scale along the object. Put a straight ruler parallel to the length. For an intact ruler, align one end with the zero mark, not automatically with the edge of the ruler.
2. Read directly above the endpoint. Look straight down at the mark under the far end. Reading from the side can make the endpoint appear aligned with the wrong mark.
3. Subtract when zero is unavailable. If the beginning of a ruler is damaged, align the object with a clear mark. An object from 2 cm to 9 cm is 9 − 2 = 7 cm long.
4. Measure a curve in sections or with thread. For a drawn curved path, lay a flexible thread along the curve without stretching it. Mark its endpoints, straighten it gently, then measure the marked length.

Worked example: A card begins at 3.2 cm and ends at 11.7 cm on a ruler. Its length is 11.7 − 3.2 = 8.5 cm. Repositioning it from 0 to 8.5 cm gives the same result.

1. A pencil runs from 2 cm to 8 cm on a ruler. Its length is…

   1. 10 cm · 2. 8 cm · 3. 6 cm

2. Where should your eye be when reading the endpoint?

   1. Directly above the mark · 2. Far to one side · 3. Below the table

3. How can a flexible thread help measure a curved drawing?

   1. Stretch it as much as possible · 2. Lay it along the curve, then measure its marked length · 3. Count the knots without using a unit

Discuss: Draw a curved path on paper. Estimate its length, measure it with a non-stretchy thread, and record how you kept the thread on the path.

Lesson 3 · Describe motion using a reference

Explain motion relative to a named reference and recognise different paths.

Name or initials: ____________   Date: ____________

A statement about motion needs an object, a reference and a change over time. The reference can change the description.

1. Choose a reference object. Describe an object’s position relative to something named. A toy bus may change position relative to a building.
2. Compare at two times. If the position relative to the reference changes with time, the object is moving relative to that reference. A passenger seated in the bus can stay at rest relative to the bus while moving relative to the road.
3. Name the path. A point can follow a straight path or a circular path. For circular motion, the path curves around a fixed centre. A turning object can include points with different paths.
4. Recognise a repeating swing. Back-and-forth motion about a central position is oscillatory. A swing returns through its path repeatedly. The sketch shows positions, not a real-time measurement.

Worked example: At 9:00, a toy bus is 20 cm from a fixed sign. At 9:01 it is 65 cm from that sign, on the same side of the sign and the same straight line. Its position changed by 65 − 20 = 45 cm relative to the sign. This evidence supports a statement of motion relative to the sign.

1. A passenger sits still in a moving bus. Relative to the seat, the passenger is…

   1. at rest · 2. always oscillating · 3. moving in a circle

2. Which observation best identifies motion relative to a tree?

   1. The object is red · 2. Its position relative to the tree changes over time · 3. The tree has leaves

3. The tip of a clock’s rotating second hand follows which path?

   1. Always a straight line · 2. No path at all · 3. A circular path around the clock centre

Discuss: Observe a clock’s second-hand tip or a safe toy. Name your reference and describe the path. Do not step onto roads or moving vehicles to make observations.

Final check · Set 1

Try one set after the lessons. Use the other set after reviewing any errors.

1. Convert 3 m to centimetres.

   30 cm / 300 cm / 3000 cm

2. Which unit is suitable for a distance between towns?

   mm / cm / km

3. A strip starts at 4 cm and ends at 13 cm. How long is it?

   9 cm / 13 cm / 17 cm

4. Which method best measures a curved pencil line?

   Stretch a rubber band hard / Place thread along the curve and measure it without stretching / Measure only the straight gap between endpoints

5. A seated passenger is moving relative to…

   the seat they stay on / their bag held still / a tree beside the road as the bus passes

6. A playground swing moves back and forth. This is…

   oscillatory motion / only straight one-way motion / no motion

Final check · Set 2

Try one set after the lessons. Use the other set after reviewing any errors.

1. Convert 70 mm to centimetres.

   700 cm / 7 cm / 0.7 cm

2. Two students get different counts using their feet. What improves comparison?

   Use the same standard unit / Choose the taller student’s guess / Remove every unit from the answer

3. A card lies from 1.5 cm to 6.5 cm. Its length is…

   8 cm / 6.5 cm / 5 cm

4. The zero edge of a ruler is broken. A valid method is…

   Always use the final reading alone / Start at a clear mark and subtract that reading / Guess because no ruler can work

5. What must change to show motion relative to a bench?

   Position relative to the bench over time / Only the object’s colour / Only the observer’s opinion

6. The tip of a fan blade turning about a fixed centre traces…

   a straight path forever / a stationary point / a circular path