Forces and Momentum

• What are the main topics covered in HL IB Physics regarding Forces and Momentum?

  Free-Body Diagrams, Newton’s Laws, Contact and Non-Contact Forces, Friction, Hooke's Law, and more
• What is the purpose of Free-Body Diagrams in physics?

  To represent forces acting on an object in a simplified manner

  
• How are forces represented in Free-Body Diagrams?

  Forces are represented by arrows indicating magnitude and direction

  
• Where should point particles be placed in Free-Body Diagrams?

  At the center of mass of the object
• What does the length of an arrow in a Free-Body Diagram represent?

  The magnitude of the force
• What information can Free-Body Diagrams provide about forces?

  They show multiple forces acting on one object, their directions, and magnitudes

  
• What are the rules for drawing a Free-Body Diagram?

  • Represent the object as a point mass
  • Include only the forces acting on the object
  • Draw forces in the correct direction
  • Use proportional magnitudes for the forces
  • Clearly label each force

  
• What are the most common forces applied in Free-Body Diagrams?

  Weight, Tension, Normal Reaction Force, Frictional Forces

  
• What does it mean for forces to be balanced?

  It means the forces cancel each other out, resulting in a zero resultant force
• What is a resultant force?

  The vector sum of all forces acting on a body
• What happens when the resultant force acting on an object is zero?

  The object is either at rest or moving at a constant velocity

  
• In a tug-of-war, what does it mean if the forces are unbalanced?

  It means there is a non-zero resultant force acting on the object
• How can you determine the resultant force in a one-dimensional situation?

  By combining the vectors of all forces acting on the object
• What is the significance of the direction defined as positive or negative when calculating resultant forces?

  It helps in determining the overall direction of the resultant force
• How do you calculate the resultant force using Pythagoras' theorem?

  By using the formula $F =$$\sqrt{F_x^2 + F_y^2}$
• What does Newton's First Law state about a body at rest?

  A body will remain at rest unless acted on by a resultant force
• What is required to change the motion of an object according to Newton's First Law?

  A resultant force is required to change the motion
• What is translational equilibrium?

  It is when the resultant force acting on an object is zero
• How can forces be split for easier analysis?

  Forces can be split into horizontal and vertical components
• If a car is moving at a constant velocity with no external forces acting on it, what can be said about the frictional force?

  The frictional force is equal to the driving force
• Why might Newton's First Law seem counter-intuitive for an object moving at constant velocity?

  Because it suggests that balanced forces allow for motion
• What is the resultant force when it is zero?


  It means the forces are balanced.
• Why is it easier to split forces into horizontal and vertical components?

  Because force is a vector quantity.

  
• What does it mean when forces are balanced?

  • Forces acting to the left equal forces acting to the right.
  • Forces acting upward equal forces acting downward.
• What is the resultant force?

  The resultant force is the vector sum of all forces acting on a body.
• If a car is moving at a constant velocity, what can be said about the frictional force?

  The frictional force is equal to the driving force.
• What does a resultant force cause?

  A resultant force causes an acceleration.
• What happens to an object if the resultant force acts along its direction of motion?

  The object will speed up (accelerate).
• What happens if the resultant force acts at an angle to the direction of motion?

  The object will change direction.
• What type of quantity is force?

  Force is a vector quantity.
• How can the magnitude and direction of the resultant force be found if it acts at an angle?

  By combining vectors or using scale drawings.
• What is acceleration?

  Acceleration is a vector quantity with both magnitude and direction.
• What does a positive resultant force indicate about acceleration?

  The acceleration is positive.
• What happens when a resultant force opposes the direction of motion?

  The object will decelerate.
• What is the effect of drag forces on a falling object?

  They cause the object to decelerate.
• What is the acceleration of a falling object independent of?

  It is independent of its mass.
• What did astronauts on the Moon demonstrate about falling objects?

  That they hit the ground at the same time regardless of mass.
• What is the upward thrust produced by the rocket in the worked example?

  15 MN.
• What is the weight of the rocket in the worked example?

  8 MN.
• What is the force due to air resistance acting on the rocket?

  500 kN.