forces and energy

• what is a system?

  a single object or a group of objects that your interested in
• 3 ways that energy systems can be changed

  by heating

  by forces doing work

  by electrical equipment
• work done (J) = force (N) x distance (M)
• how can you convert between joules (J) and newton-metres (Nm)?

  when 1 joule of work is done when a force of one newton causes an object to move a distance of one metre
• a mechanical process becomes wasteful when it causes an increase in temperature
• power is the rate of energy transfer, measured in watts, and is the rate of work done per second
• power (W) = work done (J) / time (s)
• friction is a contact force
• what force causes the repulsion of two like electrical charges?

  Electrostatic force
• what is an interaction pair?

  a set of two forces that are in opposite directions, have equal magnitudes and act of different objects
• what is a free body force diagram?

  A diagram that shows the forces acting on an object.
• what is meant by the resultant force acting on an object?

  Net force
• what is the resultant force on an object in equilibrium?

  Zero
• moment is a turning effect of a force
• moment (Nm) = force (N) x distance (m)
• what is the principle of moments?

  when a body is balanced, the total clockwise moment about a point equals the total anticlockwise moment about the same point
• levers make it easier to do work as they increase the distance from the pivot at which a force is applied