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# Science P2 Topic 4

### Edexcel GCSE additional science physics: momentum, energy, work and power

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

What is the stopping distance and what is it made up of? | The stopping distance is the distance covered from when you realise you have to stop to when the breaks bring the vehicle to a halt- it is made up of the thinking distance + the braking distance |

What is the thinking distance and how do you calculate it? | Thinking distance is the distance covered from when you realise you have to stop to when you react and hit the breaks- thinking distance = driver's reaction time X speed of vehicle |

What is the braking distance? | The distance covered from when the breaks are pressed to when they bring the vehicle to a halt |

What factors affect the stopping distance? | * driver's reaction time (affected by fatigue, drugs, illness) * condition of the road surface * condition of the tyre * friction between the tyre and road surface * speed of the vehicle * mass of the vehicle |

What is momentum? | The amount of mass in motion or how difficult it is to stop a moving object, measured in kg.m/s |

Is momentum a vector or scalar quantity and why? | A vector quantity as it has a size and a direction (the direction of the velocity) |

What is the conservation of linear momentum? | The idea that momentum is conserved at collisions |

100kg skateboarder travels at 5m/s, crashes into stationary trolley with 10kg mass- if the skateboarder keeps going in the same direction at 2m/s, what is the speed of the trolley after the collision? | 30 m/s |

What are some examples of vehicle safety measures and what do they try to do? | all vehicle safety measures try to reduce the rate of change of momentum to reduce the force of the crash on the passenger: seat belts, crumple zone, air bags |

Why is bubble wrap used? | It is used to pack fragile items as it decreases the rate of change of momentum when dropped, because the bubbles slowly compress, reducing impact |

What is needed to change the momentum? | A force (equal to the rate of change of momentum) |

What is work? | Work is done when energy is transferred from one form to another, measured in joules |

What is power in relation to work? | Power is the rate of doing work, measured in watts |

1 watt = ? (in relation to work) | 1 joule of work per second |

how do you calculate how much work must be done to stop a vehicle? | work done = braking distance X braking force |

What is the work done to stop a moving vehicle equal to? | The initial kinetic energy |

What is gravitational potential energy? | Energy that is stored due to an objectâ€™s position in a gravitational field |

What is the strength of the gravitational field strength on earth? | 10 N/kg |

What is kinetic energy? | Movement energy |

For a falling object: the initial amount of gravitational potential energy = ? | The kinetic energy when the object hits the ground |