Final answer:
In the metric system lab, a scale or balance is used to measure the weight of an object, not a ruler. Rulers measure length, while scales provide precise and accurate measurements of mass in units like grams and kilograms.
Step-by-step explanation:
In a metric system lab, when you need to determine the weight of an object, such as a pencil, you would commonly use a scale or a balance, not a ruler. Rulers are appropriate for measuring length or distance in units such as inches, centimeters, or millimeters. However, weight measurement requires an instrument capable of quantifying mass, and for that purpose, a digital scale that measures in units of mass such as grams, kilograms, or pounds is typically employed.
These scales offer more precise and accurate measurements, especially in scientific contexts where precision is crucial. For example, the weight of an apple or a violin would be best measured using a scale, indicating the mass of the item in grams or kilograms. Similarly, the weight of smaller objects, like a pencil, which weighs more than a paperclip but less than a kitten, would be measured in grams for precision.