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 happens when a force causes an object to rotate about a pivot?

  The object will rotate in the direction of the applied force.
• Give an example of rotation caused by a force.

  A child on a see-saw.
• What is a couple in terms of forces acting on an object?

  A couple consists of two equal and opposite forces acting on an object without passing through the same point.
• What is the definition of a moment in physics?

  A moment is defined as 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 = moment in newton metres (Nm), F = force in newtons (N), d = 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 if 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 about a pivot equals the total anticlockwise moment about that 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 a child on a see-saw?

  Moment = F × d, where F is the child's weight and d is the distance from the pivot.
• How do you calculate the total anticlockwise moment from an adult on a see-saw?

  Moment = F × d, where F is the adult's weight and d is the distance from the pivot.

  
• What is the relationship between the clockwise and anticlockwise moments for a balanced see-saw?

  They are equal.

  
• How do you find the distance the child must sit from the pivot for balance?

  Rearrange the equation 140 × d = 207 to find d.
• What is the distance the child must sit from the pivot if the adult weighs 690 N and sits 0.3 m from the pivot?

  d = $\frac{207}{140} =$$1.48 \text{ m}$
• What should you ensure when calculating moments in an exam?

  All distances should be in the same units and the correct forces should be considered as clockwise or anticlockwise.
• What is the function of levers in physics?

  Levers increase the size of a force acting on an object to make it turn more easily.
• What can forces cause objects to do besides rotating?

  Forces can cause objects to speed up, slow down, change direction, and deform.
• How can you make a lever work better?

  By increasing the size of the force applied or increasing the distance of the force from the pivot.

  
• How does a bottle opener function as a lever?

  A bottle opener amplifies a small force applied by a person to create a large force upwards on the bottle top.

  
• 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 to remove the cap.
• 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.
• 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 an example of rotation caused by a force?

  A child on a see-saw.
• What is the effect of a small force applied at a large distance from a pivot?

  It can create a large moment.

  
• 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 forces are equal and opposite.
• How do gears function in relation to levers?

  Gears multiply the effect of a turning force using moments.
• What are gears made of?

  Gears consist of wheels with toothed edges that rotate on an axle or shaft.
• What is a moment defined as?

  The turning effect of a force about a pivot.

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

  M = F × d

  
• What happens when one gear turns?

  The other gear must also turn in the opposite direction.
• What do the variables in the moment equation represent?

  M = moment in newton metres (Nm), F = force in newtons (N), d = perpendicular distance in metres (m).
• How does the size of a gear affect its moment?

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