forces & energy (SP8)

• what is the equation for work done?

  Work done = force x distance(moved in direction of force)
• what is weight?

  The force exerted on an object due to gravity.
• what is mass?

  the amount of matter than an object is made up of.
• what is gravitational field strength?

  a force where by one object is pulling on another object and it is pulling back.
• what is the equation for force?

  force = mass x acceleration
• what is the relationship between force and acceleration?

  directly proportional
• what is the relationship between mass and acceleration?

  inversely proportional
• what is Newton's 1st law?

  an object will change velocity if a resultant force acts on it.
• what is power?

  rate of energy transfer
• what type of forces act in a forcefield?

  non-contact forces
• what is a scalar quantity?

  magnitude only
• what is a vector quantity?

  magnitude and direction
• what are examples of scalar quantities?

  Time, temperature, mass, distance, speed.
• what are examples of vector quantities?

  Force, velocity, acceleration, displacement, weight.
• what are examples of contact forces?

  Friction, tension, air resistance.
• what are examples of non-contact forces?

  Gravity, magnetic, electrostatic.
• what is a field?

  the area around an object where it can exert a force on another object.
• when is an electric field created?

  around any externally charged object
• what does the larger the power of an object mean?

  the more work it does per second.
• what does a force doing work often cause?

  a rise in temperature as energy is dissipated to the thermal energy stores of the moving object and its surroundings. This means that the process is wasteful and the efficiency of the process is reduced.
• what is the equation for efficiency?

  useful energy transferred by device/total energy supplied to device
• what happens when a force moves an object through a distance?

  work is done on the object and energy is transferred
• what when a force does 'work' on an object?

  energy is transferred mechanically from one store to another.
• when is one joule of work done?

  when a force of one newton causes a object to move a distance of one metre (1J=1Nm)
• what are the 4 things energy can be transformed by?

  • heating
  • electrical work
  • waves
  • mechanical work
• when is more work done?

  • when you push with the same force for a longer distance
  • when you push with a larger force for the same distance
• what is the equation for energy?

  energy = potential difference x current x time
• what is the equation for power?

  power = work done / time