5.1.7 Free Body Diagrams

• What is a free body diagram?

  A free body diagram is a simple diagram that shows all the forces acting on a single object.
• How is the object represented in a free body diagram?

  The object is represented by a dot or a simple shape, like a box.
• What do the arrows in a free body diagram represent?

  The arrows represent each force acting on the object, with direction indicating force direction and length indicating force magnitude.
• What are the steps to draw a free body diagram?

  1. Identify the object you are analyzing.

  2. Identify all the forces acting on the object.

  3. Draw the object as a dot or a box in the center.

  4. Draw arrows to represent each force, pointing in the correct direction.

  5. Adjust the length of the arrows to represent the relative magnitude of each force.

  6. Label each force with its name or symbol.
• What is the force due to gravity acting on an object called?

  Weight (W)
• What is the support force exerted by a surface called?

  Normal force (N)
• What is the force that opposes motion called?


  Friction (f)
• What is the pulling force exerted by a string, rope, or cable called?

  Tension (T)
• What is any external force applied to the object called?

  Applied force (F)
• What is the force that opposes an object moving through the air called?

  Air resistance (R)
• What are the forces acting on a book on a table?

  • Weight (W): Acting downwards due to gravity.
  • Normal Force (N): Acting upwards, exerted by the table to support the book.
• What are the forces acting on a box being pushed across the floor?

  • Weight (W): Acting downwards.
  • Normal Force (N): Acting upwards.
  • Applied Force (F): Acting horizontally to the right.
  • Friction (f): Acting horizontally to the left, opposing the applied force.
• In the free body diagram of a book on a table, why are the arrows for weight and normal force the same length?

  Because the forces are balanced, meaning the book is in equilibrium and not moving.
• In the free body diagram of a box being pushed, what does it indicate if the applied force and friction are equal?

  It indicates that the box is moving at a constant speed.
• How can you determine the motion of an object using a free body diagram?

  • Balanced Forces: Equal length arrows indicate the object is at rest or moving at constant velocity.
  • Unbalanced Forces: One arrow longer than the opposite indicates the object will accelerate in the direction of the resultant force.
• What are some practical applications of free body diagrams?

  • Physics Problems: Essential for solving motion, forces, and energy problems.
  • Engineering and Design: Used to design structures and machines.
  • Everyday Situations: Helps explain phenomena like sliding, falling, or remaining stationary.
• What is the summary of free body diagrams?

  • Visual tools representing all forces acting on an object.
  • Steps to draw: Identify forces, draw the object, represent forces with arrows, and label them.
  • Analyze to determine if forces are balanced or unbalanced and predict motion.