LECTURE 1
ENGINEERING MECHANICS – science that deals with effects of forces on physical bodies
1. STATICS - effects and distribution of forces on rigid bodies which are and remain at rest
2. DYNAMICS – motion of rigid bodies caused by the forces acting upon them
a. KINEMATICS – deals with the pure motion of rigid bodies without considering the applied
forces
-“by how much does the motion change?”
b. KINETICS - relates the motion to the applied forces
-“how did the motion change?”
FUNDAMENTAL CONCEPT AND DEFINITION
PARTICLE - an object of very small size
BODY - composed of a system of particles that makes up an object of considerable size
SPEED – a scalar quantity; the time rate at which the particle covers a distance. It does not consider the
direction of motion
VELOCITY – a vector quantity; the time rate of change in displacement. It considers direction of motion
ACCELERATION – time rate of change in velocity
LAW OF INERTIA
First Law of Motion
“A particle originally at rest, or moving in a straight line with constant velocity, will remain in this state
provided the particle is not subjected to an unbalanced force.”
𝑭=𝟎
LAW OF FORCE AND ACCELERATION
Second Law of Motion
“A particle acted upon by an unbalanced force F experiences an acceleration a that has the same
direction as the force and a magnitude that is directly proportional to the force.”
𝑭 = 𝒎𝒂
LAW OF ACTION-REACTION
Third Law of Motion
“The mutual forces of action and reaction between two particles are equal, opposite and collinear.”
𝑭𝑨𝑩 = −𝑭𝑩𝑨