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# P4.2 - Circular moti

### Circular Motion - OCR A2 Physics

Question | Answer |
---|---|

Define gravitational field: | An area in which objects with a mass experience a force. |

Define electric field strength: | Force per unit charge. |

Define one radian: | One radian is the angle made at the centre of a circle, by an arc whose length is equal to the radius of the circle. |

Define centripetal force: | The force needed to keep an object moving in a circle. |

What four things can centripetal force be provided by? | Tension, gravitational force, friction and normal reaction. |

How is centripetal acceleration described? | Acceleration is the rate of change of velocity. Velocity is a measure of direction as well as speed, and the direction is constantly changing if an object is moving in a circular shape. |

What are the only two forces acting on a conical pendulum? | Tension and the objects weight. |

What is Newton's law of gravitation? | The force of attraction is PROPORTIONAL to the product of the masses, and INVERSELY PROPORTIONAL to the square of their separation. |

What is a geo-synchorinesed satellite? | Stays above the same point on the Earth. Orbits around the equator, with a period of 1 day. They must also travel from west to east. |

Define field: | The region in which a force operates. |

What does Keplar's 3rd law state? | The period of a planet squared = the radius of it's orbit cubed. |

What are geo-stationary satellites used for? | Telecommunications. |

What is a low-level satellite and what is it used for? | They orbit the Earth much lower, usually 500km. They are used for weather satellites, spy satellites and GPS. |

Define Simple Harmonic Motion: | A repeated motion where acceleration is proportional to displacement and in the opposite direction. (Think of a pendulum) |

Define displacement: | How far and in what direction the point is from it's equilibrium position. |

Define amplitude: | Maximum displacement of a point from it's equilibrium position. |

Define frequency: | The number of oscillations passing a point per second |

In a SHM oscillator, what remains constant? | Kinetic Energy + Potential Energy = Constant |

Define Resonance: | When the driving frequency is equal to the natural frequency of an oscillator, the amplitude of the oscillations increases. |

Define free oscillations: | SHM with a constant amplitude and period, with no external influences. |

Define Damped oscillations: | SHM with a decreasing amplitude and varying period due to external forces. |

Define Forced oscillations: | SHM with the oscillator being driven externally. |

What is an example of resonance? | Barton's Pendulum, microwave ovens cause the water molecules in food to resonate. |

What are examples of damping? | Bridge damping, shock absorbers in cars use critical damping. |