CP7 & CP8

• What are some ways in which the energy of a system can be changed?


  Energy can be transferred by heating, by forces doing work, or by electrical equipment.
• How is energy transferred by heating?

  Energy is moved into the thermal energy stores of the system, increasing their temperature.
• How is energy transferred by a force doing work?


  A source of energy applies a force to the system, transferring energy from one store to another.
• What happens when a box is lifted off the floor?

  Work is done against gravity, transferring energy to the box's kinetic and gravitational potential energy stores.
• How is energy transferred by electrical equipment?


  Electrical devices transfer energy between different energy stores.
• What is the equation for work done?


  Work done = force x distance moved.
• What does power mean in terms of energy transfer?


  Power is the rate of energy transfer, indicating how much work is being done every second.
• What is the rule linking joules and newtons?


  One joule of work is done when a force of one newton causes an object to move a distance of one metre.
• What effect does a gravitational field have on objects?


  A gravitational field causes attraction between objects due to their interacting fields.
• What are the effects of magnetic fields on objects?


  Interacting magnetic fields cause attraction or repulsion between magnetic objects.
• What are contact forces?

  Contact forces occur when objects are touching and a force is acted upon them.
• What are the effects of electrostatic fields on objects?


  Electrostatic forces cause attraction and repulsion between electrical charges due to interactions between their electric fields.
• What happens when objects affect each other?

  An interaction pair occurs whenever two objects interact, and both feel an equal but opposite force.
• Give two examples of vector quantities.


  Velocity and acceleration.
• Give two examples of scalar quantities.


  Speed and distance.
• What is a scalar quantity?


  A scalar quantity has magnitude but no direction.
• What is a vector quantity?


  A vector quantity has both magnitude and direction.
• How do you resolve forces into components?


  By drawing it on a scale grid and adding the horizontal and vertical components along the gridlines.
• What is the net force?


  The net force is the overall force acting on an object.
• How do scientists use scale drawings to determine the net force on an object?


  They draw all forces acting on an object to scale and measure the resultant force's length and angle.
• What happens when several forces act on an object?


  They can be replaced by one single force known as the resultant force.
• What is the energy associated with movement?

  Kinetic Energy.
• What type of energy is received by your ears?

  Sound.
• What sort of energy is given off by fluorescent objects?


  Light.
• What type of energy is stored in stretched objects?

  Elastic Potential.
• What type of energy is found in the nuclei of atoms?

  Nuclear.
• What type of energy is found in objects raised off the ground?

  Gravitational Potential.
• What type of energy is given off by hot objects?

  Thermal/Heat.
• What type of energy is carried by electrons carrying a charge?


  Electric.
• What type of energy is found in bonds between substances?

  Chemical.
• What is the unit for energy?


  Joules (J).
• What is the equation to calculate gravitational potential energy of an object raised off the ground?

  1. P.E (J) = mass (kg) x gravitational field strength (N/kg) x height (m).
• What is power in terms of energy transfer?


  Power is the rate at which energy is transferred or the rate at which work is done.
• How do you calculate power?

  Power = Energy transferred (J) / time (s).
• What is power measured in?


  Watts (W).
• What is the law of conservation of energy?


  Energy can be transferred usefully, stored, or dissipated, but cannot be created or destroyed.
• How do you calculate efficiency using energy output?


  Efficiency = Useful output energy transfer / total input energy transfer.
• What are the characteristics of scalar and vector quantities?


  • Scalar: has a size (magnitude) only (e.g., speed).
  • Vector: has size (magnitude) and direction (e.g., velocity).
• How do you calculate kinetic energy?

  Kinetic energy = $\frac{1}{2} \times \text{mass} \times \text{velocity}^2$.
• What do gravitational fields do?


  Gravitational fields attract all objects with mass.