- An objected lifted off the floor gains potential energy (often called gravitational potential energy.
- The added height gives it potential to do work when it falls.
POTENTIAL ENERGY = MASS x ACCELERATION x CHANGE IN HEIGHT
- The energy an object has because it's moving (if it's moving it's got kinetic energy)
KINETIC ENERGY = 1/2 x MASS x VELOCITY SQUARED
- The amount of energy in an electrical appliance.
ELECTRICAL ENERGY = VOLTAGE x CURRENT x TIME
Conservation of Energy
- The principle of conservation of energy says energy cannot be made or lost only changed from one form into another.
- Wind: the force of wind turns the blades of a wind turbine which causes a generator to spin and produce electricity:
- kinetic energy >> (wind turbines) >> kinetic energy >> (generator) >> electrical energy
- Water: water stored in reservoirs above a power station produces GPE. Flows through pipes to drive turbine:
- kinetic energy >> (turbine) >> kinetic energy >> (generator) >> electrical energy
- When a force moves an object, work is done on the object, resulting in a transfer of energy: work done = energy transferred
WORK DONE = FORCE x DISTANCE MOVED
- The rate of doing work. The greater the power, the more work is being done each second.
- Power is measured in watts (W) or joules per second (J/s)
POWER (W) = WORK DONE (J) / TIME TAKEN (s)
- If you swing a rubber ball attached to a piece of string in a horizontal motion at a constant speed the direction of the ball is always changing.
- This means the velocity of the ball is also changing (velocity only) so the ball must be undergoing constant acceleration.
- Newtons law connects force with acceleration: force = mass x acceleration.
- The acceleration comes from a resultant force which acts on the ball keeping it moving in a circular path which is called a inward centripetal force.
- The same principle is applied the the moon and satellites in orbit around earth and earth around the sun.
- The inward force is greater if: the mass increases, the speed/velocity increases, the radius of the circle decreases
- If the force suddenly stops (the string snaps) the object moves off in a straight line at a tangent in the circle.
- Speed, acceleration, force and energy describe how a rollercoaster works.
- The initial lift (lift hill) builds up GPE.
- After reaching it's highest point, the rollercoaster starts down the first hill where gravity takes over and the GPE changes into kinetic energy.
- Gravity and the mass of the cars/passengers apply a constant downward force which makes the cars accelerate down the hill.
- The more GPE built in the initial lift, the more kinetic energy is produced for the rest of the ride and the faster the speed of the ride.
- A rollercoasters energy is constantly changing from GPE to KE.
- Most GPE at the top of the first lift hill (lowest speed).
- As they drop, the GPE is being transferred into KE.
- The cars accelerate to reach their highest speed (max. KE) at the bottom of the slope.
- As the cars climb up the other sides, KE in transferred back into GPE.
- Einstein's theory of relativity is E = m x c x c
- The relativity theory refers to the idea that time and space are relative concepts.
- The Special and General Theories were proposed by Albert Einstein and extended the work of Isaac Newton.