5.4 Moments, Levers & Gears

• What can forces cause objects to do besides rotating?

  Speed up, slow down, change direction, deform
• How can a system of forces cause rotation?

  By acting on one side of a pivot
• What are the two types of rotation mentioned?

  Clockwise and anticlockwise

  
• What is a couple in terms of forces?

  Two equal and opposite forces acting on an object
• What is defined as the turning effect of a force about a pivot?

  Moment
• What is the equation for calculating the moment of a force?

  M = F × d
• What does M represent in the moment equation?

  Moment in newton metres (Nm)
• Why is the door handle placed opposite the hinge?

  To increase the perpendicular distance to the pivot
• What happens if the handle is close to the pivot?

  It requires more force to open the door
• What are the units of a moment?

  Newton metres (Nm)
• What does the principle of moments state?

  Total clockwise moment equals total anticlockwise moment
• What should the forces be in relation to the distance from the pivot?

  Perpendicular
• In a balanced beam, what does the equation represent?

  Total clockwise moments = Total anticlockwise moments
• How do you calculate the distance the child must sit from the pivot on a see-saw?

  Using the principle of moments

  
• How do you find the distance of the child from the pivot?

  d = 207 ÷ 140
• What is the distance the child must sit from the pivot for balance?

  1.48 m
• How is clockwise defined?

  Direction the hands of a clock move
• What do levers and gears do?

  Transmit and amplify rotational effects of forces
• How do levers increase the size of a force?

  By acting further from the pivot
• How does a bottle opener work as a lever?

  It amplifies a small force to remove a cap

  
• What does a crowbar do as a lever?

  Exerts a large force to lift heavy objects

  
• How do gears multiply the effect of a turning force?

  Using moments with toothed edges
• What happens when one gear turns?

  The other gear must also turn
• What direction do two gears rotate in relation to each other?

  In opposite directions
• How does the size of a gear affect the moment?

  Larger gears have a larger moment
• What happens when a larger gear is driven by a smaller gear?

  The large gear rotates slower but has a greater moment
• What happens when a smaller gear is driven by a larger gear?

  The smaller gear rotates quicker but has a smaller moment
• Why does the turning force on a larger gear act further from its pivot?

  Because of the gear's size
• What is the relationship between gear size and moment?

  Larger gears have a larger moment
• What is a pivot?

  A fixed point around which objects rotate

  
• What does it mean for forces to be balanced?

  They do not cause a change in motion
• What is the role of a pivot in rotation?

  It is the point around which rotation occurs

  
• How do balanced forces affect rotation?

  They do not cause rotation