ENGR 245: Mechanics Overview

Definition of Mechanics

  • Mechanics: Science that describes and predicts the motion or rest of bodies under the action of forces.

Systems of Units

  • International System of Units (SI):

    • Length: meter (m)
    • Mass: kilogram (kg)
    • Time: second (s)
    • Force: newton (N)
    • Gravity Acceleration: g = 9.81 m/s²

  • US Customary System (UCS):

    • Length: foot (ft)
    • Mass: slug
    • Time: second (s)
    • Force: pound (lb)
    • Gravity Acceleration: g = 32.2 ft/s²

Fundamental Principles

  • Parallelogram Law for Addition of Forces: Two forces can be represented by a single resultant force through a parallelogram.
  • Principle of Transmissibility: Equilibrium or motion conditions of a rigid body remain unchanged if a force is replaced by another of the same magnitude and direction at a different point.

Newton’s Laws of Motion

  1. First Law: A particle remains at rest or in uniform motion unless acted upon by a non-zero resultant force.
  2. Second Law: A particle's acceleration is proportional to the resultant force acting on it (F = ma).
  3. Third Law: For every action, there is an equal and opposite reaction.

Newton’s Law of Gravitation

  • Two masses attract each other with forces of equal magnitude and opposite directions,
  • Force: F = G(Mm/r²) where G is the gravitational constant.