3.0.0. INSTRUMENTS FOR MEASURING DISTANCE:

3.0.0.  INSTRUMENTS FOR MEASURING DISTANCE:
The instruments for measuring distance are :
I) Meter rule.    II)  Callipers   III) Vernier calliper.   IV)    Micrometre screw gauge.   Etc.

3.1.0.  METER RULE:
Meter rule is used to measure distance on paper. It is calibrated in millimeters, centimeters, . some meter rules are calibrated in inch or feet. The accuracy of meter rule is 0.1 cm or 1.0 mm.

DIDIAGRAM OF METER RULE:


3.1.2.  HOW TO MEASURE DISTANCE WITH METER RULE:
Distance is measured starting from the zero reference mark of the meter rule to any required length.  The measured distance or length is read and recorded.

3.2.0.  CALLIPERS:
Callipers are not used to measure distance or length directly as the case is in meter rule. The claws of the callipers are adjusted to touch the edges of the object that is being measured. The span of the jaws of the callipers is then measured against a calibrated scale or meter rule to determine or estimate the size of the measured distance or length.

3.2.1.   IMAGES OF CALLIPERS:

3.3.0.  VERNIER CALLIPER:
Vernier calliper is used to measure small distance.

3.3.1.  DIAGRAM OF VERNIER CALLIPER:

A Vernier calliper has two scale : the main scale and the Vernier scale.

3.3.2.  MAIN SCALE:
The calibrations or scales of the main scale of Vernier callipers vary depending on the range of measurement that the Vernier callipers are meant to measure. I will not center on the main scale.

3.3.3.  VERNIER SCALE:
The vernier scale of a vernier calliper is obtained by dividing a 9mm length into 10 equal divisions or intervals such that each divisions is 0.9mm or 0.09cm.

3.3.4.  ACCURACY OF VERNIER CALLIPER :
The accuracy of a vernier caliper is 0.1mm or 0.01cm. This means the that the smallest distance that a vernier calliper can measure is 0.1mm or 0.01cm

3.3.5.  ACCURACY OF AN INSTRUMENTS :
Accuracy of an instrument is the smallest distance (or value of a particular quantity) that the instrument can measure correctly.

3.3.6.  STEPS TO FOLLOW WHEN READING A VERNIER CALLIPER:
Step I.
Read and record the reading of the main scale
Step II.
Read and record the reading of the vernier scale at the point where the main scale and the vernier scale coincide.
Step III.
Multiply the reading of the vernier scale by the accuracy of the vernier scale which is 0.01cm.
Step IV.
Add the result of step III to the main scale reading of step I to get the final answer which is the reading of the vernier calliper.

Worked Example 1:
What is the reading of the vernier calliper as shown in the figures below?
Figures of vernier calipers.

Solution:
Reading of main scale.           =     10.0   cm
Reading of vernier scale        =     2                  
Reading of vernier scale x accuracy of vernier calliper  =                               2 x 0.01 cm  =    0.02   cm
Add the result of step III and step I to get the reading.       =    10.0 cm + 0.02 cm
Therefore,

Rcm ding of vernier calliper is  10.02cm              

 Worked Example 2:
Estimate the reading of the vernier calliper as shown in the figure below:

Solution:
Reading of main scale.           =     4.3   cm
Reading of vernier scale        =     5                  
Reading of vernier scale x accuracy of vernier calliper  =                               5 x 0.01 cm  =    0.05   cm
Add the result of step III and step I to get the reading.                                                                                                               =    4.30 cm + 0.05 cm

Therefore,     Reading of vernier calliper is  4.35 cm.    

EXERCISES:
what are the readings of the vernier callipers as shown in the figures below?.
1.                                                           2.  

 . 

3.                                              4.

5.                                                                                                       6          

 7.