Work and Power

Work and Power

1. Gravitational Potential Energy (GPE)

   • This is the the energy that weight gains
   • When an object hits the ground all of its GPE is converted into kinetic energy
   • Change in GPE = mass of object x gravitational field strength x distance raised
   • When we lift an object it is gaining GPE

2. Meteorites and kinetic energy

   • The amount of energy possessed by a moving object depends on its speed and its mass
   • A meteor is an example of kinetic energy being converted to heat and light by the friction produced between the air and the object passing through it
   • Most meteors burn up before hitting the earth, but a few do reach us
     • Most ones that reach us are either minute or land in unihabited areas, but rarely there will be a large one strike where the impact can be devastating
   • KE=½mv²

3. Energy and Work

   • Energy is the ability to do work
   • Work Done= force applied x distance through which it is applied
   • Work done is equal to the amount of energy transferred
   • Unit of energy and work = joule (J)
   • 1J of work is done when a force of 1N is applied through a distance of 1m in the direction of the force

4. Power

   • The Watt = the rate of transfer or conversion of energy of one joule per second
   • Power = work done/time taken

5. Calculations using work, GPE and KE

   • work done lifting object = gain in GPE = gain in KE of the object just before hitting the ground
   • The loss of GPE is the same as the gain of KE