Forces and Motion: The Three Laws of Motion

Forces and Motion: The Three Laws of Motion

I. Understanding Newton’s First Law of Motion - The Law of Inertia:

  • Objects at rest will stay at rest, and objects in motion will keep moving in a straight line at a constant speed, unless a net force acts upon them.
  • This is known as uniform motion.
  • Inertia is the tendency for an object to resist changes in its state of motion. The more mass an object possesses, the greater its inertia.

II. Newton’s Second Law of Motion - The Law of Acceleration:

  • The acceleration of an object is directly proportional to the net force applied to it and inversely proportional to its mass.
  • It means that the net force on an object equals the mass of the object multiplied by the acceleration of the object, or F=ma.
  • This law explains how the velocity of an object changes when it is subjected to an external force.

III. Newton’s Third Law of Motion - The Law of Action and Reaction:

  • This law states that for every action, there is an equal and opposite reaction.
  • It means that any force exerted on a body will create a force of equal magnitude but in the opposite direction on the object that exerted the first force.
  • A practical example can be the propulsion of a rocket. The action is the gas being expelled downward, and the reaction is the rocket being thrust upward.

IV. Concepts associated with Newton’s laws of motion:

  • Force: It’s a push, pull or twist that has the ability to change an object’s state of motion.
  • Mass: It’s the amount of matter present in a body.
  • Acceleration: It is how quickly the velocity of an object is changing.
  • Net force: It is the sum of all the forces acting on an object.
  • Friction: It is the force that opposes the motion of an object and acts parallel to the surfaces in contact.

V. Investigating Motion:

  • Free body diagrams can be used to illustrate physical forces acting on an object.
  • Equations of motion, or SUVAT equations, are used to calculate unknown factors such as displacement, velocity, acceleration, and time when an object is under constant acceleration.
  • Displacement-time graphs and velocity-time graphs are used to analyse the motion of an object.