Republic of the Philippines
UNIVERSITY OF RIZAL SYSTEM
Tanay – Main Campus
Tanay, Rizal
COLLEGE OF SCIENCE AND EDUCATION
General Physics
Unit 1 – Measurements, Physical Quantities and Units
This handout will help you demonstrate your understanding and skill in solving measurement problems
involving conversion of units as well as expressing it in scientific notation. Since Physics and
measurement are inseparable, measurement entails accuracy and precision. This module emphasizes
the difference of the two; accuracy and precision and illustrates its equal importance in taking
measurement.
This handout will help you explore the basic concepts on topics that will help you solve measurement
problems in the succeeding topics in Physics.
Conversion of Units
Sometimes it is necessary to convert units from one measurement
system to another or convert within a system (for example, from
kilometers to meters). Conversion factors between SI and U.S.
customary units of length are as follows:
Like dimensions, units can be treated as algebraic quantities that
can cancel each other. For example, suppose we wish to convert
15.0 in. to centimeters. Because 1 in. is defined as exactly 2.54 cm,
we find that:
where the ratio in parentheses is equal to 1. We express 1 as 2.54 cm/1 in. (rather than 1 in./2.54 cm) so that
the unit “inch” in the denominator cancels with the unit in the original quantity. The remaining unit is the
centimeter, our desired result.
Unit Consistency and Conversion of Units
There are two major systems of units in the world namely; SI (derived from French Syteme
Internationale) units also known as Metric system and the English system. Although the system of units
used by engineers and scientists is the metric system since 1960, some countries continue to use
the English system of units like for example the United States of America. However, the conversions
between the SI unit and English system of units have been well-defined.
Prefixes Used with SI Units
Multiplying and/or dividing units just like ordinary algebraic expressions give an easy way to convert
a quantity from one unit to another to be dimensionally consistent.
Example:
Example No. 01:
Convert 5 Megameter to meter
Example No. 02:
Example No. 03:
More Examples:
1.
On an interstate highway in a rural region of Wyoming, a car is traveling at a speed of 38.0 m/s. Is
the driver exceeding the speed limit of 75.0 mi/h?
Given: Speed of the car: 38.0 m/s
Speed Limit: 75.0 mi/h
Required: Is 38.0 m/s exceeds the speed limit?
Solution:
(1) Convert meters in the speed to miles:
(2) Convert seconds to hours:
Answer:
2.
The driver is indeed exceeding the speed limit and should slow down.
What if the driver were from outside the United States and is familiar with speeds measured in
kilometers per hour? What is the speed of the car in km/h?
Answer: Using the final answer in item no. 01, we now convert as:
References/Websites:
2020. Nebula2.Deanza.Edu. http://nebula2.deanza.edu/~lanasheridan/4A/RulersVernierCalipers-Mircometers.pdf.
2020. 4.Files.Edl.Io. https://4.files.edl.io/cc9f/08/26/18/225914-021efdd7-e111-4f98- 85645388f1bf7d14.pdf.
2020. Mlbgsd.K12.Pa.Us.
https://www.mlbgsd.k12.pa.us/cms/lib/PA09000085/Centricity/Domain/83/lab__accuracy_and_precision.pdf.
"Measurement, Accuracy And Precision Of Data | Grant Instruments". 2020. Grant Instruments.
https://www.grantinstruments.com/measurement-accuracy-and- precision-of-data.
"Multiple Choice Questions Answers - Online Quiz Tests". 2020. Mcqslearn.Com.
https://www.mcqslearn.com/.
"New Page 1". 2020. Pstcc.Edu.
http://www.pstcc.edu/departments/natural_behavioral_sciences/Web%20Physics/
Experiment%2001web.htm.
"Precision And Accuracy". 2020. Science Learning Hub.
https://www.sciencelearn.org.nz/resources/1880-precision-and-accuracy.