Measurement: Part 1

Measurement of Bucket

Objective : To carry out measurements of different attributes of a bucket

Introduction

Measurement is essential for any scientific study . Any scientific theory is not acceptable until and unless it is verifiable by appropriate measurement . All physical quantities are measurable . In SI system , there are seven basic physical quantities - length , mass , time , temperature electrical current , temperature and amount of substance and rest all can be derived by suitably combining one or more of these basic quantities To measure any physical quantity we need its unit and a number which

br tells us how many times the measured value is with respect to the unit For example for length we have meter as SI unit . We also need an instrument to measure a physical quantity . There is a scale associated with any measuring instrument and this scale has a least count , which is nothing but the minimum division on the scale . Because the least count is a finite value , therefore , there is an error associated with any measurement , which is nothing but plus and minus one half of the least count . Besides , we carry out various mathematical operations like addition , subtraction , multiplication , division etc . on the measured values and accordingly the errors also get combined . In this exercise we will carry out measurement of different attributes like weight , volume length , area etc . of a bucket . A bucket is a truncated conical container , which is used for storing a liquid - mainly water . Its volume V is given by following formula (Derivation of all these formulae is presented in Appendix 1 (1 (2 (3 (5

Materials : A bucket , nonstretchable strings , measuring scale , measuring tube , a spring balance

Procedure

cm

Weight of the bucket was measured by using a spring balance having least count of 0 .05 kg-wt

Role of Approximation in Measurement

Because , there is a finite least count associated with any measuring instrument , therefore , one has to resort to approximation , while measuring any physical quantity . Here we will discuss measurement of the top diameter of the bucket . The measurement is done using a measuring scale . The measuring scale one meter long , it has 100 main divisions at 1 cm distance and each main division has 10 subdivisions , each subdivision is 1 mm or 0 .1 cm long . While measuring the diameter of the bucket at the top , one end was kept at `0 ' mark on the measuring scale and the other end was lying between the marks 35 .9 and 36 .0 on the scale . Now the question is what value should be assigned to the top diameter of the bucket . Here approximation comes to our help . The gap between 25 .9 and 36 .0 is mentally divided in 10 equal parts and then it is decided as to which of these marks (in our mind ) coincides the other end . As it appeared to coincide to the 5th mark so the measured value of the top diameter was taken as 35 .95 mm . Because , we are not sure about the accuracy...