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.
