Measure before making — Engineering, 4–6 years
Measuring tells us how long, wide or tall something is. Engineers measure before cutting or joining parts, so the pieces fit instead of relying on a guess.
Numbers help parts fit
A measurement compares a thing with a unit, such as centimetres. You can measure a block, a gap or a piece of string and write down the number. That number helps you make another part the right size.
Why measure?
Before rulers and measuring tapes, people often had to guess whether parts would fit. A small mistake can leave a shelf too long, a wheel too wide or a bridge with a gap. Measuring gives builders a shared way to check sizes before they cut, drill or join.
A box on a shelf
You want a box to fit on a shelf. First, place the ruler’s zero at one end and read 30 centimetres at the other end of the shelf. Next, measure the box: it is 28 centimetres long. The box fits, with 2 centimetres left over, so it should not push against the sides.
Start at zero
A common mistake is to put the end of an object at the 1-centimetre mark and then read the number at the other end. The object will seem 1 centimetre longer than it is. This feels reasonable because the ruler’s edge is a clear place to start, but the useful starting mark is zero.
Measuring in the real world
Carpenters measure boards before cutting them, and people measure a room before buying furniture. A tailor measures a person so clothes are not too tight or too loose. Even building a toy track works better when its pieces are measured before they are joined.
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