PHY 032

• Mechanics is the area in physics which deals with the motions of macroscopic objects- objects that are large enough for us to observe without instrumentation.
• Forces applied to objects result in Displacement, or changes in the position of the objective relative to its environment. These forces can be long-ranged forces or contact forces.
• Long-range forces do not require the two forces to be touching. Example of this is Gravity.
• Contact forces exist only if the objects are touching each other. An example is a ball kicked by a person's foot.
• Force is any influence capable of changing the motion of a body. It is a push or pull.
• Forces is expressed in Dynes(CGS/Centimeter-Gram-Second), Newton (MKS/Meter-Kilogram-Second) and Pound(English Units).
• Scalar: quantities specified with magnitude only is a scalar. Examples of Scalar are length, mass, area, volume, time, and density.
• Vector: quantities specified with magnitude and direction is a Vector. Examples of vector quantities are displacement, force, velocity, acceleration and momentum.
• Vector Quantities:

  • Displacement
  • Force
  • Velocity
  • Acceleration
  • Momentum
• Scalar Quantities:

  • Length
  • Mass
  • Speed
  • Volume
  • Time
  • Density
• Components of Vector and Unit Vectors:

  • Rectangular Components >of vector are its projection on a set of right axes.
  • Component Method >of adding vectors is to resolve each into its rectangular components, which are then added, and the resultant found.
  • Resultant >is the vector sum of two or more factors.
• There are three ways to identify Vector Direction:

  1. Quadrant Bearing
  2. True Bearing
  3. Standard Position
• Quadrant Bearing:

  • vector is between 0° and 90° east or west of the north-south line.
  • first, decide whether the arrow is closer to north or south. next, decide whether it's closer to the east of the west. finally, measure the angle.
• True Bearing:

  • it is always measured clockwise from the north-south line.
  • true bearing are always given in three digits.
• Standard position:

  • is measured counter clockwise from 0°
• Equilibrium: a body is in equilibrium when there is no change in its motion.
• when a body is in Equilibrium, the vector sum of all forces acting on it is equal to zero. this is also known as the first condition for Equilibrium. that is, $∑Fₓ =$$0 and ∑Fy =$$0$
• For a system of forces to be in equilibrium, the sum of all the moment or torque is equal to zero. that is the second condition for equilibrium.

  that is, $∑M₀ =$$0$
• a Unit Vector is a dimensionless vector having a magnitude of only one. Unit Vectors are used to specify a given direction and have no other physical significance.
• the symbols i, j and k are used to represent unit vectors pointing in the positive x, y and z directions, respectively.
• Motion: the most obvious and most common phenomena of the universe around us is Motion.
• Mechanics, the foundation of physics, is classified into two branches, Kinematics and Dynamics.
• Kinematics is that branch that deals with a description of motion only, without involving the factors which tend to cause changes in the motion of bodies.
• Dynamics includes a study of the factors, like forces and physical properties of the bodies, which affect the motion of these bodies.
• Rectilinear Motion is the study of motion of bodies, or the kinematics of particles, moving along a straight line.
• Speed is distance per unit time, and velocity is the displacement per unit time.
• Instantaneous velocity is the time rate of changes in displacement.
• Acceleration is the change of velocity per unit time.
• Instantaneous acceleration is the time rate of change of velocity.
• Uniformly accelerated motion is defined as the motion in a straight line in which the distance is always the same and the speed changes at a constant rate.
• Freely Falling Body is a body that acted on by no force or no appreciable magnitude other than its weight.
• Projectile is a body which is given an initial velocity and then allowed to move under the influence of gravity only.
• Two types of Projectile motion:

  >Along the x-axis: uniform velocity, which is responsible for the particle's horizontal(forward) motion.

  >Around the y-axis: uniform acceleration, which is responsible for the particle's vertical(downward) motion.
• Uniform Circular Motion is the simplest type of motion in which the direction changes in uniform circular motion in which there is no change in speed but only a change in direction.
• Horizontal Circular Motion: a very good example of uniform circular motion is a stone tied to string and whirled around in a horizontal circle at a constant speed along the circle, such as that it completes equal number of revolutions in equal intervals of time.
• Vertica Circular Motion: if the stone is whirled in a vertical motion, the force of gravity will have to be considered in determining the tension in the string.
• Conical Pendulum: as the mass m moves with constant speed v along the circle, the cord sweeps out a conical surface, hence called conical pendulum.
• Banking curves: when a car turns around a curve, there must be a centripetal force acting on it.
• Inertia is the tendency of a body to resist any attempt to changes it velocity. "a body at rest, remains at rest."
• Mass(m) is that property of an object that specifies how much resistance an object exhibits to changes in its velocity and SI unit is kg(MKSO), g(CGS) and slug in U.S customary system.