Measurements

Measurements

Measuring Flat Surfaces Measuring tools used: Rulers or measuring tapes Things to note: Parallax error- Happens when the object is not at same level as the markings on the scale. Solution – Position eye perpendicularly at the mark of the scale. Measuring Objects without Flat Sides Using a ruler to measure an object which have no flat sides may be inaccurate. So, is there a way to measure those kinds of objects accurately? The answer is yes. Measuring object without flat surfaces requires the help of special tools. The tools are such as vernier calipers and micrometer screw gauge. They can be used to measure the diameter of marbles or plastic pellets and many more round objects. Using vernier calipers and micrometer screw gauge is also a lot more precise than the meter rule or the measuring tape. The meter rule or measuring tape has an accuracy of up to 0.1cm while the vernier caliper has an accuracy of up to 0.01cm and the micrometer screw gauge has an accuracy of up to 0.01mm. Vernier Calipers Inside jaws are used to measure the internal diameter Outside jaws are used to measure the external diameter So, if you are supposed to find the thickness of a metal tube, how are you going to find it? Solution: observed external diameter – observed internal diameter = thickness of metal tube Below is a picture that will teach you how to use a vernier caliper Accuracy of 0.01 cm Micrometer Screw Gauge Sleeve reading to largest reading you can see. Thimble reading to 2 decimal points Observed reading = Sleeve reading + thimble If reading on the thimble shows 5, the actual reading should be 0.05 mm Zero errors + zero – reading is slightly in front of zero by about 0.01cm. Solution: minus the zero error from the observed reading. - zero – reading is slightly behind of zero by about 0.01cm. Solution: add the zero error to the observed reading. Measuring Time Tools used: Stopwatches There are two kinds of stopwatches, the analogue and the digital stopwatch. The digital stopwatch is more accurate as the accuracy is 0.01s while the accuracy of the analogue stopwatch is 0.1s Human error: There is one thing to take note when using stopwatches. It takes time for the human body to react to press to timer, thus the timing may not be accurate. Another way to measure time other than the stopwatches is to use the ticker tape timer. The only timer that is used in certain physics experiments. It has a steel strip that vibrates 50 times a second and makes 50 dots a second on a paper that is pulled past it, which means that there are 50 dots made every second. Do note that the counting of time start from zero from the strip of paper. Below is an example of a ticker tape timer. I have come to the end of explaining measurements in science.

Reflections
After learning the correct way to make measurements, I now know how to make measurements as accurately as possible, avoiding parallax errors. I have also learnt how to use special tools such as the vernier calipers and the micrometer screw gauge. I have also learnt that time can not only be measured by watches, it can also be measured using a ticker tape timer.