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# SpeedingUp

### about speeding up

Question | Answer |
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In the first three seconds Mary’s acceleration is constant. Use the slope of the graph to calculate its size in metres per second squared. | |

What distance does Mary fall in the first three seconds? | |

As Mary falls she notices that her acceleration decreases until she reaches terminal velocity. At what time has she reached terminal velocity? | |

Explain why you chose this time for when Mary reaches terminal velocity. | |

In a distance, time graph down is positive so to get to terminal velocity you would have to have a constant slope. | |

Using Newton’s Second Law, explain why Mary must have no net force acting on her when she is falling at a constant velocity? | |

Mary has a mass of 65 kg. Calculate the size of the force of gravity acting on her as she falls. | |

On the diagram of Mary sketch vector arrows to represent the forces on her when she is falling at terminal velocity. | |

Deduce the size of the air resistance force acting on Mary when she falls at terminal velocity. | |

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What is the minimum work that the engine of the plane has to do to reach this height? | |

In reality, the engine has to do more work than this for the plane to reach 5000m. Explain why this is the case. | |

If the plane is flying at a speed of 60 ms-1, use the formula Ek = ½mv2 to calculate how much kinetic energy it has. | |

If the plane were to have a catastrophic engine failure and ‘fall out of the sky’ while 4 flying at 60 ms-1, ignoring air resistance, how fast would it be going just as it hit the ground? | |

On another trip a plane does 2.40 x 107 J of work to reach the jump height. It takes 10 minutes to get to this height. What power must the plane engine have to do this? | |

At sea level air pressure has a value of 1.01 x 105. Use the formula P = F/A to obtain units for pressure. | |

When Mary is at 5000m air pressure has dropped to 5.00 x 105 Pa. What sized force will a 1 cm x 1 cm area of Mary’s skin feel due to the air? |