# Unit 1: Measurements Measurement of Length.

## Presentation on theme: "Unit 1: Measurements Measurement of Length."— Presentation transcript:

Unit 1: Measurements Measurement of Length

What are we learning today?
Instruments used to measure length Accuracy / Precision Errors Vernier calipers Micrometer Screw Gauge

Instruments to measure length
Measuring tape is used to measure the distance a ball thrown. Metre rule is used to measure the length and breadth of a table. Vernier calipers is used to measure the diameter of a coin/rod. Micrometer screw gauge is used to measure the thickness of papers.

Accuracy / Precision Precision / Accuracy of an instrument is the smallest unit it can accurately measure.

Instruments used to measure length
Accuracy / Precision Instruments used to measure length Precision / Accuracy Measuring tape 0.1 cm Metre rule Vernier calipers 0.01 cm Micrometer screw guage 0.001 cm / 0.01 mm

Errors Parallax Error Human Zero Error Instrument

Errors To avoid parallax error:
The eye must be positioned vertically above the mark on the scale. Several readings and the average must be taken.

Vernier Calipers Vernier calipers consist of a main scale and a sliding vernier scale.

Vernier Calipers Vernier calipers are used to measure the internal diameters, external diameters and depth of an object.

Vernier Calipers The procedure of reading a vernier calipers:
Read the main scale opposite the zero mark of the vernier scale. This will give value up to one decimal place. Look out for the vernier mark that coincides with the marking on the main scale. This will give the value for the second decimal place.

MAIN SCALE VERNIER SCALE 2 3 1 Step 1 Step 2

Step 1 Step 2 Step 1: Reading = 0.1_ cm Step 2: Reading = 0.15 cm

Step 1 Step 2 Step 1: Reading = 4.1_ cm Step 2: Reading = 4.17 cm

Step 1 Step 2 Step 1: Reading = 2.5_ cm Step 2: Reading = 2.55 cm

Step 1 Step 2 Step 1: Reading = 0.8_ cm Step 2: Reading = 0.84 cm

Micrometer Screw Gauge
Micrometer screw gauge is used to measure anything less than 1 cm and is too small for the vernier calipers to measure.

Micrometer Screw Gauge
The procedure of reading a micrometer screw gauge: Read the main scale at the edge of the thimble. This will give value up to one decimal place in millimetres. The thimble scale has 50 divisions, each of which is 0.01 mm. Look out for the thimble mark that coincides with the datum line. This will give the value for the second decimal place in millimetres.

Step 1: Reading = 0.2__ cm Step 2: Reading = cm Step 1 Step 2

Step 1: Reading = 0.35_ cm Step 2: Reading = cm Step 2 Step 1

Step 1: Reading = 0.1__ cm Step 2: Reading = cm Step 1 Step 2

Step 1: Reading = 0.15_ cm Step 2: Reading = cm Step 1 Step 2

Pop Quiz #1 A piece of paper is m long, 35.2 mm wide and 1.5 mm thick. What is the appropriate instrument for measuring (a) the length, (b) width and (c) thickness? Which instrument can be used to measure the internal diameter of a measuring cylinder?

Similar presentations