Question Video: Measuring Length Using a Vernier Caliper Physics

What is the length of the object being measured by the Vernier caliper in the diagram?

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Video Transcript

What is the length of the object being measured by the Vernier caliper in the diagram?

In order to find the length of an object being measured by a Vernier caliper, you must place the object within its jaws, as seen in the diagram here. We can then start reading the markings on the side of the caliper itself. The markings near the top that look like a ruler are called the main scale. And the markings on the bottom along the lower jaw of the calipers itself is called the Vernier scale. Measuring on the main scale is just like measuring on any other ruler. The large labeled marks represent whole numbers, and the smaller marks in between them are portions of those whole numbers. In this case, each smaller portion represents one-tenth of one of the whole numbers. For example, this marker here represents 1.9 because it is one-tenth smaller than two, which it is closest to.

But reading objects on the main scale of a Vernier caliper works slightly differently. Because the object we want to measure is in the jaws of the caliper, there is a discrepancy between where the object starts and where the scale starts. When measuring using a Vernier caliper, we don’t start where the object starts, but rather instead where the Vernier scale says zero. This means to actually measure on our main scale, we have to look at it like this, where the main scale is visible with the Vernier scale. This is because we want to find the marking that is closest to the left of this zero marking, which appears to be this one right here.

To get what number this is, let’s start at our closest whole number to the left, in this case two. Then, we count from there: one, two, three, four, five, six, seven. So, since each of these smaller markings represents one-tenth, this means that this line here represents 2.7.

We can still see though that there is a small, small difference between these two lines here. And that difference is going to be given to us using the Vernier scale, which is more accurate. The Vernier scale, again present on the lower jaw of the caliper, measures in one-tenths of the one-tenths, which is to say on the one one hundredth scale. Each of these markings represents one one hundredth. The marking that we care about though is the one that most closely aligns with the lines above it in the main scale. In this case, this is nine over here, where we can see that the lines most closely match up there compared to anywhere else. This means that the Vernier scale is telling us to add nine one hundredths, which in decimal is 0.09 centimeters.

The length of the object is, thus, found by combining the values we got from the main scale with the value that we got from the Vernier scale. So it’s just 2.7 centimeters plus 0.09 centimeters, which gives us the answer of 2.79 centimeters.

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