topic 9 - forces and effects

• How does gravitational attraction depend on mass?

  The larger mass gives greater attraction
• What happens with electrostatic attraction/repulsion?

  Like charges repel, opposite charges attract
• How does charge size affect electrostatic force?

  A larger charge gives greater force
• What is the effect of a stronger magnet?

  A stronger magnet gives a stronger field
• What do like poles do in magnetism?

  Like poles repel each other
• What is the normal contact force?

  Force perpendicular to the plane of contact
• What causes friction between surfaces?

  Rough surfaces cause friction when moved
• What defines a vector?

  A vector has size and direction
• What is a scalar?

  A scalar has just size
• What do free body diagrams represent?

  • Direction of forces present in a situation
  • Helps visualize forces acting on an object
• How does the reaction force act?

  At the normal to the line of contact
• In which direction does friction act?

  Opposite to the direction of movement
• How does weight act on an object?

  Weight always acts downwards
• What does the length of an arrow in a scale drawing represent?

  Size of the force in relation to others
• What happens when arrows in a scale drawing are equal in length but opposite in direction?

  The forces cancel out, object is in equilibrium
• What occurs when weight and air resistance are equal for a skydiver?

  No resultant force, terminal velocity is reached
• What forces act on a skydiver initially?

  Only weight
• What happens to air resistance as a skydiver accelerates?

  Air resistance increases with speed
• What is the relationship between thrust and air resistance in a vehicle at terminal velocity?

  Thrust is balanced by drag and friction
• What happens when more thrust is added to a vehicle at terminal velocity?

  It becomes the resultant force until balanced
• What is required for rotation to occur?

  An object must be attached to a pivot point
• What happens if a force is applied not towards the pivot?

  The object will not rotate
• What is the formula for moment?

  Moment = Force × Distance
• What is equilibrium in terms of moments?


  Sum of anticlockwise moments equals clockwise moments
• How do gears affect speed and force?

  Gears can change speed, force, or direction
• What happens when a gear with fewer teeth is connected to a larger gear?

  The second gear turns faster but with less force
• What is the effect of lubrication on gears?


  Reduces friction and increases efficiency
• What are the key points about rotation and force application?


  • Force applied perpendicular causes rotation
  • Non-perpendicular requires finding perpendicular distance
  • Direction of force affects rotation