Ch1. Introduction

Ch1. Introduction

[Outline]

- Engineering terminologies & Mechanics

- Newtonain gravitation

1. Engineering terminologies & Mechanics

 

● What is Machanics?

 : Study of forces and their effects.

 

→ Statics : objects in Equilibrium

→ Dynamics : objects in Motion

 

* F=ma 

  - If there is no acceleration (a), then the force (F) belongs to the field of statics.

→ So, statics deals with forces when there is no acceleration

 

  ○ Statics : it deals with objects at rest or moving with constant velocity

  ○ Dynamics : it deals with the analysis of physical bodies in motion

● Numbers

1. significant digits (유효숫자)
   : the number of meaningful digits in a number.
   
   
2. Limited by the accuracy of the measurement.
   
   –tip! –
3. When using calculators, avoid round-off errors for intermediate results to maximize accuracy
   → 계산기 사용 시, 최대한 계산된 숫자를 모두 기입해 계산기를 돌려라!

● Space & Time

1. Space : the 3D universe by length or distance
2. Time : the interval between repeatable events
3. + Velocity (m/s), acceleration (m/s^2)

 

● Newton’s 1st law of motion

-  if the mass is constant, the sum of the forces is equal to the product of the mass of the object and its acceleration (관성의 법칙 → 움직임을 유지하려는 성질)

● Newton’s 2nd law of motion

-  if the objective is initially stationary, it will remain stationary.

● Newtons’s 3rd law of Motion

- The forces exerted by two objects on each other one equal in magnitude and opposite in direction (작용반작용 법칙 → 수직항력에 대한 개념이 탄생)

● International system of units (SI Units)

- 1N = (1kg) (1m/s^2)

  → base units :kg, m, s 

  → Force unit is not base unit / Force unit can express with base unit’s combination)