Moments, Levers & Gears

• What can forces cause objects to do besides rotating?

  Forces can cause objects to speed up, slow down, change direction, and deform.
• How can a system of forces cause rotation?

  A system of forces can cause rotation by acting on one side of a pivot.
• What are the two types of rotation mentioned?

  Clockwise and anticlockwise.
• What is an example of rotation caused by a force?

  A child on a see-saw.
• What happens if two forces act on an object without passing through the same point?

  The object can still rotate.
• What is a couple in terms of forces?

  A couple is when two equal and opposite forces act on an object.
• What is a moment defined as?

  A moment is the turning effect of a force about a pivot.
• What is the equation for calculating the moment of a force?

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

  M is moment in newton metres (Nm), F is force in newtons (N), and d is the perpendicular distance in metres (m).
• Why is the door handle placed on the opposite side to the hinge?

  To increase the perpendicular distance from the pivot, creating a larger moment.
• What happens when you open a door with a handle close to the pivot?

  It would be much harder and require more force.
• What are the units of a moment?

  Newton metres (Nm) or Newton centimetres (Ncm).
• What does the principle of moments state?

  If an object is balanced, the total clockwise moment equals the total anticlockwise moment about a pivot.
• What is the formula for calculating moments on a balanced beam?

  Total clockwise moments = Total anticlockwise moments.
• What forces cause a moment on a horizontal beam?

  Forces directed upwards or downwards.
• How do you calculate the total clockwise moment from the child on a see-saw?

  Moment = F × d = 140 × d.
• How do you calculate the total anticlockwise moment from the adult on a see-saw?

  Moment = F × d = 690 × 0.3 = 207 Nm.
• How do you find the distance the child must sit from the pivot for the see-saw to be balanced?

  By rearranging the equation 140 × d = 207 to find d = 207 ÷ 140 = 1.48 m.

  
• What is the importance of ensuring all distances are in the same units when calculating moments?

  To ensure accurate calculations of moments.
• What do levers and gears do in terms of forces?

  They transmit and amplify the rotational effects of forces.
• How do levers increase the size of a force acting on an object?

  By applying the force further from the pivot than the force it has to overcome.
• What is an example of a lever in everyday use?

  A bottle opener.

  
• How does a bottle opener use a lever to amplify force?

  It creates a large force upwards on the bottle top from a small force applied by the person.

  
• What is the role of the line of action in a lever?

  The line of action of the small force is much further from the pivot than the large force needed at the edge of the cap.
• How does a crowbar function as a lever?

  A crowbar exerts a large force to a narrow opening, making it easier to lift heavy objects.

  
• What is the effect of a small force applied at a large distance from a pivot?

  It can create a large moment.

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

  By using moments through wheels with toothed edges that rotate on an axle.

  
• What happens when one gear turns?

  The other gear must also turn in the opposite direction.
• How does the size of a gear affect the moment?

  The moment depends on the size of the gear, which changes the distance of the teeth to the pivot.

  
• What happens when a larger gear is driven by a smaller gear?

  The larger gear will rotate slower than the smaller gear but will have a greater moment.

  
• What happens when a smaller gear is driven by a larger gear?

  The smaller gear will rotate quicker than the larger gear but will have a smaller moment.

  
• Why does the turning force on the larger gear wheel act further from its pivot?

  Because it is driven by the smaller gear.
• What is the relationship between the direction of rotation of two gears that are meshed together?

  They will rotate in opposite directions.