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ASSIGNMENT NO.1 (MECH 222 - Dynamics of Rigid Bodies)

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MECH 222
Dynamics of Rigid Bodies
ASSIGNMENT NO.1
Name: VILLAGRACIA, JAY V.
Course, Yr. & Sec.: BSCE 2A
1. What is Dynamics?
Dynamics is the branch of mechanics that deals with the study of bodies in motion.
Dynamics has its origins in the Greek word dynamis, "force, power." In physics, dynamics
is the study of bodies in motion and changes in that motion, and that idea can be applied to
other areas as well. For example, we refer to "group dynamics" as the way people interact
and work together. George W. Bush once observed, "Globalization has altered the
dynamics in the White House, as well as between the White House and the Treasury."
2. What is the difference between Kinematics and Kinetics?
Kinematics is the geometry of motion. The term is used to define the motion of a
particle or body without consideration of the forces causing the motion. Kinematics is
essentially a treatment of the relations between displacement, velocity, and acceleration.
While Kinetics is the branch of dynamics that relates the force acting on a body to its mass
and acceleration. When the acceleration of a body caused by the forces acting on it has
been determined, the principle of kinematics may be applied to determine the displacement
or velocity at any instant. In other cases, the kinematic motion of a body may be used to
compute its acceleration; from this, by means of the relations to be developed later, the
force or forces required to produce this motion can be determined.
3. Enumerate and explain Newton’s Law of Motion of a Particle? Site an example for each.
Newton’s laws of motion for a particle have been stated in a variety of ways. For
purposes we shall phrase them as follows:
1. A particle acted upon by a balanced force system has no acceleration. When all the
forces acting upon an object balance each other, the object will be at equilibrium;
it will not accelerate. For example, consider a physics book at rest on a tabletop.
There are two forces acting upon the book. One force, the Earth's gravitational pull
exerts a downward force. The other force, the push of the table on the book
(sometimes referred to as a normal force) pushes upward on the book. Since these
two forces are of equal magnitude and in opposite directions, they balance each
other. The book is said to be at equilibrium. There is no unbalanced force acting
upon the book and thus the book maintains its state of motion.
2. A particle acted upon by an unbalanced force system has an acceleration in line
with and directly proportional to the resultant of the force system. This means that
the presence of an unbalanced force will accelerate a particle changing its speed,
its direction, or both its speed and direction. Consider that the car is accelerating to
the right. Therefore, the net force is to the right since the acceleration is to the right.
An object which moves to the right and speeds up has a rightward acceleration.
3. Action and reaction forces between two particles are always equal and oppositely
directed. This means that when two particles collide, both particles experience
forces that are equal in magnitude and opposite in direction. Such forces often cause
one particle to speed up (gain momentum) and the other particle to slow down (lose
momentum). Consider the collision between a moving seven ball and an eight ball
that is at rest in the sport of table pool. When the seven ball collides with the eight
ball, each ball experiences an equal force directed in opposite directions. The
rightward moving seven ball experiences a leftward force that causes it to slow.
down; the eight ball experiences a rightward force that causes it to speed up. Since
the two balls have equal masses, they will also experience equal accelerations. In a
collision, there is a force on both objects that causes an acceleration of both objects;
the forces are equal in magnitude and opposite in direction. For collisions between
equal-mass objects, each object experiences the same acceleration.
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