Question Video: Identifying How to Measure the Length of an Object That a Ruler Cannot Touch | Nagwa Question Video: Identifying How to Measure the Length of an Object That a Ruler Cannot Touch | Nagwa

# Question Video: Identifying How to Measure the Length of an Object That a Ruler Cannot Touch Physics • First Year of Secondary School

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Fill in the blanks: When measuring the length of an object that a ruler must not or cannot directly touch, the positions of the opposite ends of the object are ＿ . The object can then be ＿ and the distance between the marked points can be measured with a ruler.

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### Video Transcript

Fill in the blanks. When measuring the length of an object that a ruler must not or cannot directly touch, the positions of the opposite ends of the object are blank. The object can then be blank and the distance between the marked points can be measured with a ruler. Is it (A) exchanged and reversed or (B) marked and removed?

In this question, we are asked to figure out how we can measure the length of an object that a ruler must not or cannot directly touch and fill in the blank spots to make the sentences correct.

Let’s recall some important information when measuring with a ruler. Rulers are made from a straight strip of material with markings that are spaced out carefully. The numbers on a ruler will always start with zero and go to a greater value, increasing until the end of the ruler is reached. To measure some length, the ruler must be placed with its zero mark lining up with the end of the length being measured. Because rulers are straight, they must be set parallel to whatever length we are measuring in order to get an accurate measurement.

Let’s go back to this problem and look at the sentences we are trying to complete.

Looking at the blank spaces we need to fill in, we are trying to think of a way we can measure the object without having the ruler touch it. For the first blank space, if we exchanged the positions of the ends of the object, our ruler still cannot touch it. So this wouldn’t help us measure the length of it. For the second blank space, if we reversed the object, it would change the physical position of the object, but we still would not be able to touch it with the ruler. So neither of the words in the first option will work in these sentences.

Now let’s look at the words in the second option we were given. If we mark the positions of the opposite ends of the object, its length will be equal to the length between those marks. And then, if we removed the object, the marks of the ends of the objects would still be there. We could then use our ruler to measure the length between the marks. And because the lengths of the marks and the object are identical, we can measure the length of our object this way.

Therefore, option (B), marked and removed, is the correct answer.

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