Question Video: Identifying a Measuring Instrument for Measuring Mass Physics

Which of the following instruments is used to measure an object’s mass? [A] A thermometer [B] A weighing scale [C] An ohmmeter [D] A Geiger counter [E] A light gate

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Video Transcript

Which of the following instruments is used to measure an object’s mass? A) A thermometer, B) A weighing scale, C) An ohmmeter, D) A Geiger counter, E) A light gate.

Okay, so in this question, we’re trying to measure an object’s mass. So let’s go through all of the options one by one. Firstly, a thermometer. Well, a thermometer is a device that’s used to measure temperature. This is why it’s called a thermometer. It measures a thermal quantity, specifically temperature. So it’s not used to measure an object’s mass.

Moving on then, option B, a weighing scale. Now, a weighing scale can come in many different forms. For example, this digital weighing scale here, where we place our object on the weighing scale and the reading shows us the mass of that object. Therefore, this looks like the answer to our question. We’re measuring the object’s mass with a weighing scale.

However, just to make sure, let’s go through all the other options as well. Option C then, an ohmmeter. Well, an ohmmeter is a device used in an electric circuit to measure the resistance of a particular component in the circuit or of the entire circuit itself. The unit of electrical resistance is the ohm. Therefore, this device is called an ohmmeter. So it’s not used to measure an object’s mass.

Option D then, a Geiger counter. A Geiger counter is a device that’s used for measuring ionising radiation. The way it works is that it counts the number of ionising radiation particles passing through its detector every second. And so the reading that we get from a Geiger counter is in counts per second. In other words, how many counts of ionising radiation are there per second in the local area. So a Geiger counter also doesn’t measure mass.

And finally option E, a light gate. A light gate is most commonly a U-shaped device which fires a beam of light, usually infrared light, from one end of the U tip to the other. Now a light gate works by registering the time at which the beam gets broken by, for example, an object. This way light gates can be used for very accurate timing or, for example, an object’s motion. But because they’re used to measure time, they’re not used to measure mass.

And so we have our final answer: the instrument used to measure an object’s mass is a weighing scale.