Rollercoasters and Relativity

A set of cards with all the information for the P2 GCSE Physics module.

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Potential Energy

  • 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

         

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Kinetic Energy

  • 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

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Electrical Energy

  • The amount of energy in an electrical appliance. 

ELECTRICAL ENERGY = VOLTAGE x CURRENT x TIME

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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

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Work

  • 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

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Power

  • 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)

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Circular Motion

  • 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.
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Centripetal Force

  • 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. 
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Rollercoasters

  • 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. 
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Converting Energy

  • 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.
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Relativity

  • 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.
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