Third law and inertia

• What is inertia in physics?

  The tendency for motion to remain unchanged
• How does inertia relate to objects at rest?

  Objects at rest stay at rest until acted on
• What does Newton's First Law state about motion?

  Objects in motion stay in motion unless acted on
• What does an object's inertial mass measure?

  Difficulty in changing the object's velocity
• How is inertial mass calculated according to Newton's second law?

  Inertial mass is F divided by acceleration
• What does Newton's Third Law state about forces between two objects?

  Forces are equal and opposite
• What happens when you push a shopping trolley?

  The trolley pushes back against you equally
• What occurs when you stop pushing a trolley?

  The trolley comes to rest due to inertia
• How do action and reaction forces work in the skater example?

  Skater A pushes Skater B, both feel equal forces
• Why does Skater A accelerate more than Skater B?

  Skater A has a smaller mass than Skater B
• What does the principle of conservation of momentum explain?

  It explains equally-sized forces in opposite directions
• What happens to a book on a table in equilibrium?

  • Weight pulls the book down
  • Normal force from the table pushes up
  • Forces are equal, book does not move
• What are the forces acting on a book sitting on a table?

  The weight of the book and normal force
• What are the pairs of forces due to Newton's Third Law for a book on a table?

  Weight from Earth and book's reaction force
• What is the normal contact force acting on the book?

  The force pushing up from the table
• Why is the book's situation not an example of Newton's Third Law?

  The forces are acting on the same object
• What is an example of a pair of forces demonstrating Newton's Third Law in a car moving at constant velocity?

  The car's weight and the normal force from the road