Dynamics is the branch of mechanics that deals with the motion of objects under forces. It has two parts: kinematics, which is the study of motion without considering forces, and kinetics, which relates forces to motion. Dynamics uses concepts such as mass, force, velocity, and acceleration. Newton's laws of motion describe how forces affect the motion of objects. Problems are solved by drawing diagrams, identifying knowns and unknowns, selecting an equation, substituting values, and checking that units are consistent and answers are reasonable.

1. Dynamics is that branch of mechanics which deals with the motion of bodies under the action of forces.
Two Parts of Dynamics
1. Kinematics – study of motion without reference to the forces which cause motion.
2. Kinetics – relates the action of forces on bodies to their resulting motions.
Basic Concepts
1. Space is the geometric region occupied by bodies.
2. Time is a measure of succession of events.
3. Mass is the quantity that measure the inertia or resistance to change in motion f a body.
4. Force is the vector action of one body on another.
5. Particle is a body of negligible dimensions.
6. Rigid body is a body whose changes in shape are negligible compared with the overall
dimensions of the body or with the changes in position of the body as a whole.
7. Vector and scalar quantities. Vector quantities have magnitude and direction while scalar
quantities deal with magnitude only.
8. Newton’s Laws
Law 1: A particle remains at rest or continues to move in a straight line with constant velocity if
there is no unbalanced force acting on it.
Law 2: The acceleration of a particle is proportional to the resultant force acting on it and is in
the direction of this force.
Law 3: The forces of action and reaction between interacting bodies are equal in magnitude,
opposite in direction and collinear.
9. Fundamental units
Nomenclature S.I. Units U.S. Customary Units
Mass m kilogram, kg slug
Length l meter, m feet, ft
Time t second, s second, sec
Force F Newton, N pound, lb
Velocity v m/s ft/sec
Acceleration a m/s2 ft/sec2

2. How to solve problems:
1. Draw a neat, reasonably accurate sketch where appropriate.
2. Write down all the known quantities. If necessary, convert them to the proper units. Put these
quantities on the sketch.
3. Write down the unknown quantity (or quantities) and show it on the sketch as well.
4. Find the basic equation that connects known and unknown quantities.
5. Solve the basic equation for the unknown quantity.
6. Substitute the known quantities in the resulting formula, including all the units. If more
information was given than needed to work out the problem, which sometimes happens, one or
more of the quantities will not have to be used.
7. Carry out the indicated operations to get the answer. Be sure the units are the same on both
sides of the equal sign and that the correct number of significant figures appears in the answer.
8. Ask yourself if the answer is reasonable. Often a scale drawing can be made in Step 1 and
answer checked by a measurement on the drawing. If the units of the answer are strange to
you, you might express the answer in more familiar units to see if it makes sense.
References:
1. Engineering Mechanics: Statics and Dynamics 8th Edition by RC Hibbeler
2. Engineering Mechanics: Volume 2, SI Version, 3rd Edition by JL Meriam and LG Kraige
3. Modern Technical Physics 6th Edition by Arthur Beiser