CHAPTER 1 Physical Quantities, Units and Measurement

By the end of the lesson, you should be able to answer the following questions:  What are physical quantities?  What is the difference between qualitative and quantitative description?  Why are units so important in presenting a reading?  What is the difference between scalar and vector quantities?  Give examples of scalar and vector quantities  What are the Base Quantities in Physics and what are their SI units?

Physical Quantities  A property that can be measured and is presented with magnitude and unit.  Look into your textbook contents page, what do you think are the quantities that is measured in each chapter?  Examples – mass, weight, speed, density, time, volume, area, length etc

Quantities, Magnitude, Units  The weight of a coin is 12 g. Quantitymagnitude unit

Qualitative vs Quantitative Observations  Qualitative – Descriptive  Quantitative – Use numbers Describe the mass of the apple qualitatively.  The apple has a large mass. Describe the mass of the apple quantitatively.  The apple’s mass is 50 g.

No NAKED numbers please!!! Do these numbers make sense to you? What do they lack? x 10 8

Scalar and Vectors  Scalar – A physical quantity with magnitude  Vector – A physical quantity with magnitude and direction

How to remember which one has direction? Vector

Are they scalars or vectors?  Distance  Force  Energy  Temperature  Weight  Mass  Velocity Stand up if you think it is a Vector Remain seated if you think it is a Scalar

Base Quantities and its Unit  Length – meter (m)  Mass – kilogram (Kg)  Time – seconds (s)  Electrical current – ampere (A)  Temperature – kelvin (K)  Amount of substance – mole (mol)  Luminous intensity – candela (Cd)

Derived Quantities  Speed = Distance ÷ Time Derived quantity Basic quantity

Can you answer the following questions:  What are physical quantities?  What is the difference between qualitative and quantitative description?  Why are units so important in presenting a reading?  What is the difference between scalar and vector quantities?  Give examples of scalar and vector quantities  What are the Base Quantities in Physics and what are their SI units?