engphyslec

• Physics


  Deals with fundamental concepts like time, motion and force, space, matter, energy, gravity, and radiation. It also deals with the transformation of matter and energy.
• Measurement


  Comparison of an unknown quantity with a known standard amount of the same quantity. It is also the process of getting the actual measure of an object's dimension or property by comparing it with something that has been accepted as a standard unit.
• Systems of Measurement


  • English or British System
  • Metric System
• Types of Metric System

  • MKS (m, kg, s)
  • CGS (cm, g, s)
• Kinds of Physical Quantities

  • Fundamental Units - direct measurement
  • Derived Units - known by computations
• Conversion of Units


  Key idea is to express the same physical quantity in two different units and form an equality
• Scalar


  Quantities with magnitude only
• Vector


  Quantities with both magnitude and direction
• Unit Vector


  A dimensionless vector one unit in length used to specify a given direction. Unit vectors have no other physical significance. They are used simply as a convenience in describing a direction in space.
• Mechanics


  The study of the motion of objects and the related concepts of force and energy.
• Kinematics

  The quantitative description of an object's motion
• Dynamics


  Deals with why objects move as they do
• Motion


  A continuous change of position with respect to a specific time frame of reference during a given time.
• Time (t)


  Motion always takes place over a period of time. Time is normally measured in seconds or in other related units, such as minutes or hours.
• Displacement


  A vector that points from an object's initial position to its final position and whose magnitude is equal to the distance separating the points. It is only the straight-line distance from the starting point to the present location.
• Position


  Defined in terms of a frame of reference. It is one-dimensional.
• Displacement


  Vector quantity
• Free falling body


  A body falling under the action of its weight done.
• The acceleration of a free falling body is due to gravity at sea level, 45o latitude.
• Projectile


  A body projected by external force and continuing in motion by its inertia. It is also an object launched into space without a motive power of its own, traveling freely under the action of gravity and air resistance alone.
• In projectile motion, with no air resistance, ax = 0 and ay = 0. The coordinates and velocity components are simply functions of time, and the shape of the path is always a parabola.
• Newton's First Law: Law of Inertia


  When no force acts on a body, or when the vector sum of all forces acting on a body is zero, if it is initially in motion, it continues to move in constant velocity. The body at rest remains at rest and the body in motion remains in motion unless acted by an external force.
• If an object is travelling at constant velocity and force is added, velocity increases.
• If an object is travelling at a constant velocity and the force applied it will change its direction.
• Newton's Second Law: Law of Force and Acceleration


  The acceleration of a body is directly proportional to the force and inversely proportional to the mass being accelerated.
• Force


  Any influence that will set a body in motion
• Inertia


  Property of matter to resist motion.
• Newton


  The force that will give to a mass of 1kg an acceleration of 1m/s2
• Dyne


  The force that will give to a mass of 1gm an acceleration of 1cm/s2
• Pound


  The force that will give to a mass of 1 slug an acceleration of 1 ft/s2
• Newton's Third Law: Law of Interaction


  In every action, there is an equal and opposite reaction.
• Friction


  The resistance to movement of one body over another body. The word comes from the Latin verb "fricare," which means "to rub." It is also a tangential force on a body which opposes any tendency for its surface to move relative to another surface.
• Kinetic or sliding friction

  A tangential force between two surfaces when one body is sliding over another.
• Properties of Friction


  • The frictional force is parallel to the surface sliding over one another.
  • The frictional force is proportional to the force which is normal (perpendicular) to the surfaces and which presses them together.
  • The frictional force is roughly independent of the speed of sliding provided that the resulting heat does not alter the condition of the surfaces.
  • The frictional force depends upon the nature of the substances in contact and the condition of the surfaces (on polish, roughness, grain, and wetness)
• Static Friction


  Tangential friction between two surfaces when one is not sliding over another.
• Coefficient of static friction

  Ratio of the maximum frictional force to the normal force
• Angle of repose (limiting angle)


  Angle just before the block starts to slide.
• Uniform circular motion


  The motion of an object in a circle at a constant speed. An object is constantly changing its direction as it moves in a circle. At all instances, the object is moving tangent to the circle.
• In Newton's Law of Gravitation, it states that every body in the universe attracts every other body with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
• Uniform circular motion


  The motion at constant speed along a curved path of constant radius.