Introduction to Kinematics

Cinemática

• Cinemática studies movement without addressing its causes.
• Movement is a change in a body's position over time, relative to a frame of reference.
• Key elements to understand in kinematics include trajectory, position, distance traveled, displacement, and velocity.
• A mobile is any body that moves.

Position

• Position refers to locating an object in space.
• A frame of reference is needed to define the position of a mobile.
• A frame of reference consists of a point and a system of axes considered fixed in the universe, used to measure the distance to the object.
• The origin of coordinates is the point where the axes intersect, serving as the starting point for measurements.
  • One dimension is for linear movements
  • Two dimensions are for movements in a plane
  • Three dimensions are for movements in space
• The position of a body is the location it occupies with respect to a fixed reference frame.

Trajectory

• Trajectory is the set of points a body follows in motion.
• Trajectories can be straight or curved.
• Movements are divided into rectilinear (straight-line) and curvilinear types based on their trajectory.
  • Curvilinear includes circular, parabolic, elliptical, and oscillatory movements.

Distance vs Displacement

• The distance traveled is the length of the trajectory described, always a positive number.
  • It is a scalar magnitude.
• Displacement is the distance between the final and initial positions of a movement, represented on a straight line.
  • It is a vector magnitude with direction, sense, and module.
• Example: Juan walks 30m East, 40m North, then 30m West.
  • The total distance he traveled is 100m.
  • His displacementis 40m North.

Velocity

• Velocity in physics is defined as either medium or instantaneous.
• Average velocity is the displacement made by a mobile in a time interval, calculated by dividing displacement by time.
• Instantaneous velocity is the limit of average velocity as the time interval approaches zero.
• Rapidity (celerity) is the absolute value of velocity.
• Average rapidity is calculated similarly to average velocity, but using distance traveled instead of displacement.

Uniform vs Accelerated Motion

• Movements can be uniform or accelerated.
• Uniform motion has a constant velocity.
  • Position vs. time graph is a straight line.
  • Velocity vs. time graph is a horizontal line.
• Accelerated motion has a constant acceleration.
  • Position vs. time graph is a parabola.
  • Velocity vs. time graph is a straight line.
  • Acceleration vs. time graph is a horizontal line.
• Graphs in physics use a Cartesian system, where the x-axis represents time.