Forces, accelerations and Newton's Laws of motion

• Newton's First Law

  • If the resultant force acting on an object is zero and the object is stationary, the object remains stationary
  • If the object is moving, the object continues to move at the same speed and in the same direction so the object continues to move at the same velocity
  • So, the velocity (speed and/or direction) of an object will only change if a resultant force is acting on the object
• What is Inertia?

  • The tendency of objects to continue in their state of rest or of uniform motion
• Newton's Second Law

  • The acceleration of an object is proportional to the resultant force acting on the object, and inversely proportional to the mass of the object
• What is Inertial Mass?

  • Is a measure of how difficult it is to change the velocity of an object
  • Is defined as the ratio of force over acceleration
• Netwon's Third Law

  • Whenever two objects interact, the forces they exert on each other are equal and opposite