Key Physics Topics

  • Created by: xerinx
  • Created on: 10-03-19 13:53

Newton's First Law

  • A resultant force is needed to make something start moving, speed up or slow down
  • If the resultant force on a stationary object is zero, the object will remain stationary
  • If the resultant force on a moving object is zero, it will carry on moving at the same velocity
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Newton's Second Law

  • Acceleration is proportional to the resultant force
  • The larger the resultant force acting on an object, the more it accelerates
  • Acceleration is inversely proportional to the mass of an object
  • Therefore, an object with a larger mass will accelerate less than one with a smaller mass
  • The formula for the second law is:

F = m x a

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p = m x v

momentum(kg m/s) = mass(kg) x velocity(m/s)

  • The greater the mass or velocity of an object, the more momentum the object has
  • Momentum is a vector as it has a size and direction
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Changes in Momentum

  • A force causes momentum of an object to change
  • A resulatant force of an object causes it to accelerate ( Newton's 2nd Law)
  • Acceleration is a change in velocity over time, so:

force = mass x change in velocity / time

  • This means a force applied to an object will change its velocity
  • Mass x change in velocity is equal to change in momentum, so:

force = change in momentum / time

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Energy Stores

The types of energy stores are:

  • Kinetic
  • Thermal
  • Chemical
  • Gravitational Potential
  • Elastic Potential
  • Electrostatic
  • Magnetic
  • Nuclear
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Kinetic Energy

When an object is moving, it has energy in its kinetic energy store

You can find the energy in a kinetic energy store using:

kinetic energy = 0.5 x mass x ( speed x 2 )

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Conservation of Energy

Energy is never created or destroyed 

Energy can be stored, transferred between stores, and dissipated - but it can never be created or destroyed.

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  • Usefull devices can transfer energy from one store to a usefull store
  • However, some of the input energy can dissipate into the surroundings 

You can calculate the efficiency of any device using:

efficiency = useful energy / total energy supplied

This gives you a decimal so to find a percentage you need to multiply the answer by 100

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Energy Resources - Renewable

  • Renewable resources will never run out as they can be renewed as it is used
  • Most of them do damage to the enviroment but not as much as non-renewable resources

They include:

  • Bio-fuels
  • Wind
  • The Sun (solar)
  • Hydro-electricity
  • Tides
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Energy Resources - Non-Renewable

  • Non-renewable energy resources are fossil fuels and nuclear fuel
  • They provide the most of the worlds energy
  • They are natural resources that form underground over trilions of years
  • The main fossil fuels are oil, coal and gas
  • They emmit carbon dioxide into the atmosphere when they're burned, which adds to the greenhouse effect, and contributes to global warming
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