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# Math of Mechanics

### 2013 Chapter 3 8th grade Science

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

Mechanics | the study of motion |

What does a scalar quantity tell us? | Scalar quantities tell size OR magnitude of the thing measured |

What does a vector quantity tell us? | A vector quantity has both magnitude and direction. |

Which of these quantities is a scalar quantity, distance or displacement? | Distance is scalar; displacement is vector |

Which of these quantities is a vector quantity, Speed or velocity? | Velocity is vector; speed is scalar |

What are some other vector quantities? | Acceleration, force, and momentum |

Define Distance | How far an object has moved |

Define Displacement | Distance and direction of an object from its starting point |

Define Speed | The distance an object moves per unit of time |

Velocity | Distance and direction an object moves per unit of time |

Average speed | The average over time when speed is changing |

Instantaneous speed | Speed at any given moment in time like on your speedometer in the car |

Constant speed | Speed that is not changing or is staying the same |

Acceleration | Speed that is increasing or getting faster |

Deceleration | Negative acceleration or speed that is decreasing/slowing down |

Define Force | Any push or pull on an object |

State Newton’s First Law of Motion | When there is no unbalanced force on an object, objects at rest stay at rest and objects moving keep moving at the same speed in the same direction |

State Newton’s Second Law of Motion | When an unbalanced force acts on an object it accelerates |

What did Galileo determine about the rate of falling objects? | All objects fall at the same rate if there is little or no air resistance |

What is the acceleration of gravity at the earth’s surface? | 9.85 m/s2 |

What are 5 differences between mass and weight? | Mass is the amount of matter in something and weight is the pull of gravity. Mass is measure on a balance in g or kg and weight is measured on a spring scale in N. Mass cannot change or be zero and weight can. |

What is momentum? | Momentum is the product of mass and velocity |

How do we calculate it? | p(momentum) = m(ass) * v(elocity) |

Be able to calculate using the formula for Force | F = m* a |

Be able to calculate using the formula for momentum | p = m * v |

Advanced only: What is Impulse? | Force times time equals impulse |

Advanced only: Relate Impulse to momentum | Impulse is equal to the change in momentum. |

Advanced only: How does this relate to building safer cars? | When momentum changes quickly, Force can be minimized by extending the time it acts. Air bags, seat belts, and bumpers which crumple all work to allow extra time between the Force and its impact in a collision. |