Resultant forces

• What is the resultant force?

  A single force that has the same effect as a number of forces acting together on an object
• How do you calculate the resultant force on a straight line?

  • Add forces acting in the same direction.
  • Subtract forces acting in opposite directions.
• When is a force said to be balanced?

  If the forces acting in opposite directions are equal in size, then there will be no resultant force so they're balanced
• What are the forces involved in the example of a car driving on a road.

  • driving force acting forward
  • friction acting backwards
  • air resistance acting backwards
• What are the forces involved in the example of a skydiver falling through air.

  • weight acting downwards
  • upward force acting (due to air resistance)
• What does the length of an arrow in a free-body diagram show?

  magnitude/ size of the force
• What do free body diagrams show?

  forces acting on an object
• What happens to the object if the forces acting on it are balanced?

  • Stays at rest (if stationary).
  • Moves at a constant velocity (if already in motion).
• When should you use a vector diagram to find out the resultant force?

  • When two or more forces act at angles
  • equilibrium situations