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# Physics Ch. 4&5

### Ch. 4 and 5 study cards

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

Newton's First Law of Motion | An object stays at rest or in motion (at a constant velocity) unless another net force changes its state. Often called the Law of Inertia |

Newton's Second Law of Motion | For a given net force, the magnitude of the acceleration is inversely proportional to the mass. |

Newton's Third Law of Motion | Often called acceleration or action-reaction law; states whenever 1 object exerts a force on a 2nd object, the 2nd object exerts a opposite directed force of = magnitude on the 1st object. For every action/force, there is a =, but opposite, reaction |

Force | A force is a push or pull and is a vector quality. The SI Unit of Force is Newton or kg*m/s2 |

Mass | Mass is a property of matter that determines how difficult it is to accelerate or decelerate an object. Mass is a scalar quantity. 2)The mass of a body is a quantitative measure of inertia adn is measured in an SI unit of kg. |

Weight | W=mg; The weight of an object is the gravitational force that the earth exerts on the object. SI unit: Newton |

Free Fall | a=-g. The apparent weight is 0 b/c when both the person and the scale fall freely, they cannot push against one another. |

Weightlessness | the apparent weight is 0; apparent weight=mg +ma |

Inertia | Inertia is the natural tendency of an object to remain at rest or in motion at a constant velocity. The SI unit of Inertia and Mass is kg. |

Kinetic Friction | Kinetic Friction is usually less than Static Friction. The force of kinetic friction btw 2 surfaces sliding against one another opposs the relative motion of the surfaces. |

Static Friction | The force of static friction btw 2 surfaces opposes any impending relative motion of the surfaces. |

1 Newton (N) | =1 kg*m/s2 |

1 dyne (dyn) | = 1 g*cm/s2 |

1 slug (sl) | =1 lb*s2/ft |

1 pound (lb) | =1 ft/s2 |

Three fundamental forces | gravitational force, strong nuclear force, and electroweak force |

Normal Force | The normal force is one component of the force that a surface exerts on an onject w/ which it is in contact--nameley, the component that is perpendicular to the surface. |

Friction | The force component parallel to the surface is called friction. |

Kepler's third law | The period is proportional to the 3/2 power of the orbital radius. |