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# Physics - Mr O'Shea

### Physics - Unit 1 - OCR

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

What is the difference between a scalar and a vector? | Scalars only have size but Vectors have both size and direction. |

Name some vectors: | Displacement, force, velocity, acceleration and momentum. |

Name some Scalars: | Mass, temperature, time length speed and energy |

What does uniform acceleration mean? | Uniform acceleration is constant acceleration. |

Acceleration is the rate of change of velocity, what equation do you get from this? | V = u + at |

S = average velocity X time, from this what equation do you get? | S = (u + v)/2 X t |

Substitute v = u + at, and S = (u + v)/2, and you get what equation? | S=ut + 1/2at^^2. (^^ means squared) |

v^^2 = u^^2 + 2as. (^^ means squared) | |

What is free fall? | Free fall is when there is only gravity and nothing else. |

What did Aristotle say about heavy and light objects? | Heavy objects fall quicker than lighter objects, this did in fact turn out to be wrong, he used reasoning to get to this theory. |

What did Galileo say about objects falling? | All objects in free fall accelerate uniformly. He reckoned that the reason objects don't normally is due to air resistance. Scientists think he rolled a ball down a slope to test his theory. |

What shape graph does displacement-time give? | A curved graph. |

What does the gradient of a displacement-time graph show you? | The gradient tells you the velocity. |

If the gradient of a graph isn't constant, what does this mean about the object? | It is accelerating. |

What does the gradient of a velocity time graph tell you? | The acceleration. |

The area under a speed-time graph shows you what? | The distance travelled. |

What is the density equation? | Density = mass/volume |

What is the velocity equation? | velocity = distance/time |

Speed = distance/.... | speed = distance/time |

What are the seven base quantities? | Mass (kg), length (m), time (s), electric current (A), amount of substance (mol), temperature interval (K) |

What are the eight decimal prefix names and what is their value? | Tera (12), giga (9), mega (6), kilo (3), mili (-3), micro (-6), nano (-9) and pico (-12) |

What is uncertainty? | In one reading the uncertainty is equal to ± the smallest that instrument can measure. (e.g. ± 1mm for a ruler) |

What is the equation to work out the percentage uncertainty? | Uncertainty/reading X100% |

What is the equation to work out the percentage difference? | difference/average X 100% |

Define acceleration: | Acceleration is the rate of change of velocity. |

In the monkey and the hunter experiment, why does the bullet always hit the monkey? | They are both at the same height when they are dropped. Once they both start falling they’re under the same value of acceleration of free fall, and whilst this is happening the bullet is traveling horizontally towards the monkey until they meet. |

What is a moment? | A moment is the turning effect of a force. It depends on: - Size of the force. - Distances the force is applied from the turning point, |

What will happen if moments are not balanced? | The object will turn. For equilibrium, the moments clockwise must equal the moments anitclockwise. |

What is the equation to work out the moment of a force? | Moment of a force = Force X perpendicular distance from pivot (distance from the turning point) |