## Numerical Problems, Work and Energy

S.No | Description of numerical problem |
---|---|

Problem 1 | A 70 kg man runs up a long flight of stairs in 4 s. The vertical height of the stairs is 4.5 m. Calculate his power. See Solution |

Problem 2 | A body of mass 2.0 kg is dropped from a rest position 5 m above the ground. What is its velocity at height of 3.0 m above the ground? See Solution |

Problem 3 | A man pulls a trolley through a distance of 50 m by applying a force of 100 N which makes an angle of 300 with horizontal. Calculate the work done by the man. See Solution |

Problem 4 | The roller-coaster car starts its journey from a vertical height of 40 m on the first hill and reaches a vertical height of only 25 m on the second hill, where it slows to a momentary stop. It travelled a total distance of 400 m. Determine the thermal energy produced and estimate the average friction force on car whose mass is 1000 kg. See Solution |

Problem 5 | A man whose mass is 70 kg walks up to the third floor of a building which is 12 m above the ground in 20 s. Find his power in watt and horsepower. See Solution |

Problem 6 | To what height can a 400 w engine lift a 100 kg mass in 3 s? See Solution |

Problem 7 | A ball of mass 100 grams is thrown vertically upward at a speed of 25 ms-1. If no energy is lost, determine the height it would reach. If the ball only rises to 25 m, calculate the work done against the air resistance. Also calculate the force of friction. See Solution |

Problem 8 | An object of mass 1000 g falls from a height of 30 m on the sand below. If it penetrates 4 cm into the sand, what opposing force is exerted on it by the sand? Neglect air friction. See Solution |

Problem 9 | A body of mass m drops from bridge into water of the river. The bridge is 10 m high from the water surface. |

Problem 10 | The engine of a JF-Thunder fighter develops a thurst of 3000 N. What horsepower does it at a velocity of 600 m/s. See Solution |

Problem 11 | The mass of moon is 1/80 of the mass of the earth and the corresponding radius is 1/4 of the earth. Calculate the escape velocity on the surface of the moon. See Solution |

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