《大学物理》课程PPT教学课件：课程PPT教学课件（英文版）Chapter 1 Introduction

Chapter 1 Introduction

Chapter 1 Introduction

Theories and Experiments The goal of physics is to develop theories based on experiments a theory is aguess, expressed mathematically, about how a system works The theory makes predictions about how a system should work Experiments check the theories predictions Every theory is a work in progress

Theories and Experiments ◼ The goal of physics is to develop theories based on experiments ◼ A theory is a “guess,” expressed mathematically, about how a system works ◼ The theory makes predictions about how a system should work ◼ Experiments check the theories’ predictions ◼ Every theory is a work in progress

1. 1 Fundamental Quantities and Their Dimension Length [l] MaSs [mi Time lti other physical quantities can be constructed from these three

1.1 Fundamental Quantities and Their Dimension ◼ Length [L] ◼ Mass [M] ◼ Time [T] ◼ other physical quantities can be constructed from these three

Units To communicate the result of a measurement for a quantity, a unit must be defined Defining units allows everyone to relate to the same fundamental amount

Units ◼ To communicate the result of a measurement for a quantity, a unit must be defined ◼ Defining units allows everyone to relate to the same fundamental amount

Systems of Measurement Standardized systems agreed upon by some authority usually a governmental body SI --Systeme international agreed to in 1960 by an international committee main system used in this text also called mks for the first letters in the units of the fundamental quantities

Systems of Measurement ◼ Standardized systems ◼ agreed upon by some authority, usually a governmental body ◼ SI -- Systéme International ◼ agreed to in 1960 by an international committee ◼ main system used in this text ◼ also called mks for the first letters in the units of the fundamental quantities

Systems of Measurements cont cgs -Gaussian system named for the first letters of the units it uses for fundamental quantities US Customary everyday units often uses weight, in pounds, instead of mass as a fundamental quantity

Systems of Measurements, cont ◼ cgs – Gaussian system ◼ named for the first letters of the units it uses for fundamental quantities ◼ US Customary ◼ everyday units ◼ often uses weight, in pounds, instead of mass as a fundamental quantity

Length Units Si -meter, gs - centimeter, cm US Customary -foot, ft a Defined in terms of a meter - the distance traveled by light in a vacuum during a given time

Length ◼ Units ◼ SI – meter, m ◼ cgs – centimeter, cm ◼ US Customary – foot, ft ◼ Defined in terms of a meter – the distance traveled by light in a vacuum during a given time

Mass a Units si kilogram, kg a cgs- gram, g USC-slug, slug Defined in terms of kilogram based on a specific cylinder kept at the international bureau of Weights and Measures

Mass ◼ Units ◼ SI – kilogram, kg ◼ cgs – gram, g ◼ USC – slug, slug ◼ Defined in terms of kilogram, based on a specific cylinder kept at the International Bureau of Weights and Measures

Standard Kilogram

Standard Kilogram

Time Units seconds, s in all three systems Defined in terms of the oscillation of radiation from a cesium atom

Time ◼ Units ◼ seconds, s in all three systems ◼ Defined in terms of the oscillation of radiation from a cesium atom