Inertia and Newton’s Third Law

• Until acted upon by a resultant force, objects at rest stay at rest and objects moving at a steady speed will stay moving at that speed. This tendency to continue in the same state of motion is called inertia
• An object‘s inertial mass measures how difficult it is to change the velocity of an object.

  Inertial mass can be found using Newton’s Second Law of F=ma so inertial mass is just the ratio of force over acceleration
• Newton’s Third Law:

  When two objects interact, the forces they exert on each other are equal and opposite.