Energy

• What energy is wasted in a ball bouncing on the ground


  Sound energy and thermal energy
• kinetic energy formula


  KE=1/2mv²
• gravitational potential energy


  mass x gravitational field strength x height
• Equation for power


  work done or energy transferred / time
• energy flow diagram in a mobile phone

  
• describe the energy transferof a rock falling


  at the top if a rock is dropped from 10m, the energy at the top is the same as at the bottom, just transferred to kinetic energy while falling. at the top if the energy is 98, it would be 98j of gravitational potential energy. about halfway it would be around 49j of gpe and 49j of kinetic. At the bottom 98j of energy would be kinetic as all the energy was transferred from the gpe.

  
• types of energy

  
• chemical energy used for

  battery acids
• elastic potential uses


  trampolines, spring
• light energy uses

  lamps, lighting
• thermal energy uses

  heaters, radiators
• gravitational potential energy uses


  a yoyo before it is released, a car parked at the top of a hill
• mechanical work is when...


  when an energy transfer occurs due to a force, eg an object falls from a height and releases sound energy when in contact with the floor
• Solar energy is used to generate electricity and to produce hot water. Solar energy is energy released by nuclear fusion in the Sun. how is solar energy obtained?


  When the sun shines onto a solar panel, energy from the sunlight is absorbed by the PV cells in the panel. 
• Advantages of solar energy

  • Solar energy is a renewable energy resource and there are no fuel costs.
  • No harmful polluting gases are produced
• Disadvantages of solar energy

  • Solar cells do not work at night.
  • Solar panels may only produce very hot water in very sunny climates, and in cooler areas may need to be supplemented with a conventional boiler.
  • Although warm water can be produced even on cloudy days, solar panels do not work at night.
• how does solar panels work in houses?

  Solar panels work by using sunlight to generate electricity. They are made of many solar cells, typically silicon-based, which absorb sunlight and create electron-hole pairs. An internal electric field pushes the electrons towards one layer and holes towards another, creating a flow of direct current (DC). This DC is then converted into alternating current (AC) by an inverter, which can be used to power homes or stored in batteries.
• how can water energy be used to generate electricity?

  Like the wind, water can be used to drive turbines directly. There are several ways that water can be used, including waves, tides and falling water in hydroelectric power schemes.
• Tidal power

  Huge amounts of water move in and out of river mouths each day because of the tides. A tidal barrage (a kind of dam) is built across estuaries, forcing water through gaps to make use of the kinetic energy in the moving water. The barrage contains electricity generators, which are driven by the water rushing through tubes in the barrage.
• Wave power

  The water in the sea rises and falls because of waves on the surface. Wave machines use the kinetic energy in this movement to drive electricity generators. The movement of seawater in and out of a cavity on the shore compresses trapped air, driving a turbine.
• Hydroelectric power


  Like tidal barrages, hydroelectric power (HEP) stations use the kinetic energy in moving water. Often, the water comes from behind a dam built across a river valley. The water high up behind the dam contains gravitational potential energy. This is transferred to kinetic energy as the water rushes down through tubes inside the dam. The moving water drives electric generators, which may be built inside the dam.
• Advantages of water energy

  • Water power in its various forms is a renewable energy resource and there are no fuel costs.
  • No harmful polluting gases are produced.
  • Tidal barrages and hydroelectric power stations are very reliable and can be easily switched on.
• Disadvantages of water energy

  • It has been difficult to scale up the designs for wave machines to produce large amounts of electricity.
  • Tidal barrages destroy the habitat of estuary species, including wading birds.
  • Hydroelectricity dams flood farmland and push people from their homes.
  • The rotting vegetation underwater releases methane, which is a greenhouse gas.
• Wind turbines

  Wind turbines use the wind to directly drive turbines. They have huge blades mounted on a tall tower. The blades are connected to a nacelle, or housing, which contains gears linked to a generator. As the wind blows, it transfers some of its kinetic energy to the blades, which turn and drive the generator. Several wind turbines may be grouped together in windy locations to form wind farms.
• Advantages of wind energy

  • Wind is a renewable energy resource, meaning it will not run out.
  • There are no fuel costs.
  • No harmful polluting gases are produced.
• Disadvantages of wind energy

  • Wind farms are noisy.
  • The amount of electricity generated depends on the strength of the wind.
  • If there is no wind, there is no electricity.
  • Manufacture and implementation of wind farms can be costly.
  • Some local people object to on-shore wind farms, arguing that they spoil the countryside.
• this is a sankey diagram example, it shows the efficiency of a product and the percentages of useful and wasted energy.

  
• elastic potential energy = 0.5 × spring constant × (extension)2
• A spring has a spring constant, (k), of 3 N/m. It is stretched until it is extended by 50 cm. Calculate the elastic potential energy stored by the spring, assuming it is not stretched beyond the limit of proportionality.

  elastic potential energy = 0.5 × spring constant × (extension)2

  50 cm = 50 ÷ 100 = 0.5 m then square 0.5=0.25

  0.5x3x0.25=0.375j