Physics P2

Physics P2

Motion
1. Distance- Time Graphs
  1. Gradient represents speed
  2. Steeper the line the greater the speed
  3. Speed= Distance/ Time
2. Velocity and Acceleration
  1. Velocity- Speed in a direction
  2. Acceleration- Change in speed per second
  3. Acceleration= (Final Velocity- Initial Velocity)/ time
3. Velocity- Time Graphs
  1. Horizontal Line- No acceleration
  2. Gradient represents acceleration
  3. Area under line represents distance travvelled
4. Using Graphs
Forces
1. Forces Between Objects
  1. Measured in Newtons
  2. Exert equal and opposite forces on eachother
  3. Forces change shape and motion of an object
2. Resultant Forces
  1. Simplified force of all the forces acting on an object
  2. Acceleration shows resultant force must be acting on object
3. Force and Acceleration
  1. Bigger the resultant force, greater the acceleration
  2. Force= Mass x Acceleration
4. On the Road
  1. Friction and air resistance opposes driving
  2. Stopping Distance= Thinking Distance+ Breaking Distance
5. Falling Objects
  1. Mass is the amount of matter, but weight is gravity acting on the mass
  2. Weight= Mass x Gravitational Potential Energy
  3. Terminal Velocity- Velocity when weight equals drag
6. Stretching and Squashing
  1. Extension of a spring is difference between original length and extended length
  2. Extension of a spring is directly proportional to the force applied
7. Force and Speed Issues
  1. Improve fuel economy by reducing speed or wind resistance
  2. Speed cameras in pairs to average speed
  3. Anti-skid surfaces increase friction
Work, Energy and Momentum
1. Energy and Work
  1. Work is done when force causes object to move
  2. Work Done= Force x Distance Moved
2. Gravitational Potential Energy
  1. Depends on weight and height from the ground
  2. GPE= Mass x Gravitational Field Strength x Change in Height
3. Kinetic Energy
  1. Depends on mass and speed
  2. KE= 0.5 x mass x velocity (squared)
  3. Elastic Potential Energy stored in elastic object when work is done
4. Momentum
  1. Momentum (p)= Mass x Velocity
  2. kgm/s
  3. Momentum is conserved when objects interact
5. Explosions
  1. Objects move apart with different speeds if unequal masses
  2. Move with equal but opposite momentum so total is 0
6. Impact Forces
  1. Impact depends on mass change in velocity and duration of impact
  2. Exert equal and opposite forces on eachother
  3. Total momentum unchanged
7. Car Safety
  1. Seat belts and air bags spread force
  2. Crumple zones increase impact time
  3. Conservation of momentum used to calculate cars mass
Current Electricity
1. Electrical Charges
  1. Some insulating materials become charged when rubbed
    1. Electrons are transferred causing a charge
  2. Like charges repel
2. Electric Circuits
  1. Current= Charge (Q)/ Time
  2. Every component has own symbol
3. Resistance
  1. Volts= Work Done/ Charge
  2. Volts= Energy/ Charge
  3. Resistance= Volts/ Current
  4. Ohm's Law- Current through resistor is directly proportional voltage
4. Potential Difference Graphs
5. Series Circuits
  1. Current same at each component
  2. Pd used up. Add all pd values to find total
  3. Add resistance to find total
6. Parallel Circuits
  1. Current splits between branches depending on resistance
  2. Pd same across each branch
Mains Electricity
1. Alternating Current
  1. Direct Current travels in one direction
  2. Alternating Current changes direction
  3. Mains circuit has alternating live wire and neutral wire at 0V
  4. Frequency= 1/ Time
2. Cables and Plugs
  1. Plastic used as a coating as it is a good insulator
  2. Cables are copper wires coated in plastic
  3. Three- Pin Plug
    1. Live Wire- Brown
    2. Neutral Wire- Blue
    3. Earth Wire- Green and Yellow
  4. Earth wire used on metal cased appliances
3. Fuses
  1. Contains a thin wire that melts if too much current passes through it, shorting the circuit
  2. Circuit breaker is a switch that automatically trips but an easily be reset
4. Electrical Power and Potntial Difference
  1. Power is energy transferred each second
  2. Power= Current x Voltage
  3. Pd amount of voltage used up by each componant. Measured by a voltmeter
  4. Voltage= Work Done/ Charge
5. Electrical Energy and Charge
  1. Current is the rate of flow of charge
  2. Measured in Coulombs
6. Electrical Issues
  1. Faults can cause shocks and fires
  2. Touching a mains circuit with wet hands could cause shock
  3. Should check plugs for damage
Radioactivity
1. Observing Nuclear Radiation
  1. Radioactive substance has unstable nucleus, radiation emitted to become stable
  2. Three types
    1. Alpha
    2. Beta
    3. Gamma
  3. A random event that can't be predicted
  4. Background radiation is always present
2. Discovery of the Nucleus
  1. Rutherford used evidence from alpha scattering to deduce there was a small positively charged nucleus
3. Nuclear Reactions
  1. Isotope- Has same number of protons and different number of neutrons
4. Alpha, Beta and Gamma Radiation
  1. Alpha radiation stopped by thin paper and deflected by magnetic field
  2. Beta radiation is stopped by thin layer of metal and is deflected by magnetic field
  3. Gamma radiation can only be stopped by thick lead
  4. All radiation can strip electrons of atoms they crash into, possibly causing mutation. This is called ionisaiton
5. Half Life
  1. Average time it takes the number of unstable nuclei to halve
6. Radioactivity at work
Energy from the Nuclei
1. Nuclear Fission
2. Nuclear Fusion
3. Nuclear Issues
4. Early Universe
5. Life History of a Star
6. Formation of Elements

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