Motion

Understanding Motion

  • Motion refers to the change in position of an object with respect to its surroundings in a given period of time.
  • Motion is always measured relative to a frame of reference.

Types of Motion

  • Uniform motion: An object is in uniform motion if it moves in a straight line and covers equal distances in equal intervals of time.
  • Non-uniform motion: An object is in non-uniform motion if it travels in an irregular path or does not cover equal distances in equal intervals of time.

Speed, Velocity and Acceleration

  • Speed is the rate of change of distance with respect to time and is a scalar quantity.
  • Velocity is the rate of change of displacement with respect to time and is a vector quantity, meaning it has both magnitude and direction.
  • Acceleration refers to the rate of change of velocity with respect to time.

Graphs of Motion

  • A distance-time graph can be used to determine an object’s speed. The slope of the graph at any point gives the speed of the object at that time.
  • A velocity-time graph can be used to determine an object’s acceleration. The slope of the graph at any point gives the acceleration of the object at that time.

Forces and Motion

  • Newton’s First Law states that an object at rest tends to stay at rest, and an object in motion tends to stay in motion, with the same speed and in the same direction unless acted upon by a resultant force.
  • Newton’s Second Law states that the acceleration of an object is directly proportional to the resultant force acting on it and inversely proportional to its mass. The direction of the acceleration is the same as the direction of the resultant force.
  • Newton’s Third Law states that for every action, there is an equal and opposite reaction.

Gravity and Motion

  • Gravity is a force that attracts two objects towards each other. On Earth, gravity pulls objects towards the ground, which causes dropped objects to fall and gives everything weight.
  • The acceleration due to gravity on Earth is approximately 9.8 m/s².

Inertial and Non-inertial Frames of Reference

  • An inertial frame of reference is one in which Newton’s first law of motion holds true. Objects not acted upon by a force will maintain their state of motion.
  • A non-inertial frame of reference is one in which Newton’s first law of motion does not hold true. This is typically observed in frames that are themselves in accelerated motion.