topic 9 forces and their effects

• What are the three types of non-contact forces?

  Gravitational, electrostatic, magnetic
• What usually causes non-contact forces?

  Interacting fields
• What do interacting magnetic fields cause?

  Attraction or repulsion between magnetic objects
• What do electrostatic fields cause?

  Attraction and repulsion between electrical charges
• What is the normal contact force?

  Force acting between all touching objects
• What is the difference between a vector and a scalar?

  Vector has size and direction; scalar has size
• Give an example of a vector and a scalar.

  Vector: force; Scalar: distance
• What does a free body force diagram show?

  Isolated body and all acting forces
• What do the sizes of arrows in a free body force diagram represent?

  Relative magnitude of forces
• What does the direction of arrows in a free body force diagram indicate?

  Direction of the forces
• How can forces cause rotation?

  Force on spanner causes a turning effect
• What is a moment in physics?

  Turning effect of a force
• What happens when a larger force or longer distance is applied?

  Larger moment is produced
• How can you achieve maximum moment on a spanner?

  Push at right angles to spanner
• What happens if you push at an angle other than right angles?

  Smaller distance and smaller moment
• What is the formula for moment of force?

  Moment = force x distance
• What is the principle of moments?

  Sum of clockwise moments = sum of anticlockwise moments
• How do levers work?

  • Transfer the turning effect of force
  • Push one end down, other end rises
  • Increase distance from pivot to reduce force needed
• How do gears transmit turning effects?

  • Interlock to transmit rotational effects
  • Turning one causes another to turn opposite
  • Larger gear spins slower than smaller gear
• What is the effect of applying force to a small gear?

  Creates a small moment on the next gear
• What happens when a larger gear receives force from a smaller gear?

  Larger gear has a larger moment
• What is the purpose of lubrication in gears?

  Reduces friction and improves efficiency
• Why are gears often lubricated?

  To improve the efficiency of machines