Motion

• Motion is a change in position of an object with respect to a reference point
• Kinematics is a branch of physics that deals with the descriptive study of motion
• Quantities used to describe motion include:

  • Distance (d)
  • Displacement (d)
  • Speed (v)
  • Velocity (v)
  • Acceleration (a)
• Scalar Quantity can be completely described by its magnitude and appropriate units
• Vector Quantity requires direction in addition to magnitude and units for a complete description
• Distance is a scalar quantity that refers to the actual length of the path traveled by an object from its initial position to its final position
• Displacement is a vector quantity that refers to the straight-line distance between the initial and final position, with the direction pointing toward the final position
• Speed describes the distance per unit time and is a scalar quantity
• Speed does not indicate a change in direction and common units for speed are kilometers per hour (km/h), centimeters per second (cm/s), meters per second (m/s), and centimeters per day (cm/day)
• Velocity is similar to speed but also indicates the direction of motion, making it a vector quantity
• Acceleration occurs when velocity changes and is defined as the rate of change of velocity with time, usually measured in meters per second squared (m/s^2)
• Acceleration is positive if the speed increases, negative if the speed decreases, and zero if there is no change in speed
• Uniform motion is where velocity is constant and acceleration is zero
• Uniformly accelerated motion is where velocity changes at a constant rate, with constant acceleration throughout the motion
• Two common graphs used to describe motion are the displacement-time graph and the velocity-time graph
• A motion detector is a device that can sense motion within a certain distance, classified as long-range or short-range
• Scalar Quantity Distance Speed
• Vector Quantity Displacement Velocity
• In linear motion, a positive or negative sign is usually used to indicate the direction. 

   

  Right, upward, eastward, northward – (+)

  Left, downward, westward, southward – (-)