A block of \(1\) kg is released from the top of a smooth curve \(\mathrm{AB},\) and then it encounters a rough surface \(\mathrm{BC},\) coming to rest at \(\mathrm{C}.\) The work done by friction is:

(take \(g=10\) m/s^{2})

1. \(25\) J

2. \(50\) J

3. \(-25\) J

4. \(-50\) J

Subtopic: Â Work Energy Theorem |

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The work done by all the forces (external and internal) on a system equals the change in:

1. | total energy | 2. | kinetic energy |

3. | potential energy | 4. | none of these |

Subtopic: Â Work Energy Theorem |

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A bullet from a gun is fired on a rectangular wooden block with velocity \(u\). When bullet travels \(24\) cm through the block along its length horizontally, velocity of bullet becomes \(u/3\). Then it further penetrates into the block in the same direction before coming to rest exactly at the other end of the block. The total length of the block is:

1. \(30\) cm

2. \(27\) cm

3. \(24\) cm

4. \(28\) cm

1. \(30\) cm

2. \(27\) cm

3. \(24\) cm

4. \(28\) cm

Subtopic: Â Work Energy Theorem |

Â 67%

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NEET - 2023

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A body of mass \(1\) kg is thrown upwards with a velocity \(20\) ms^{-1}. It momentarily comes to rest after attaining a height of \(18\) m. How much energy is lost due to air friction?

(Take \(g=10\) ms^{-2})

1. \(20\) J

2. \(30\) J

3. \(40\) J

4. \(10\) J

Subtopic: Â Work Energy Theorem |

Â 87%

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AIPMT - 2009

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In a ballistics demonstration, a police officer fires a bullet of mass \(50.0\) g with speed \(200\) m/s on soft plywood of thickness \(2.00\) cm. The bullet emerges with only \(\text{10%}\) of its initial kinetic energy. The emergent speed of the bullet is:

1. \(0\)

2. \(53.2\) m/s

3. \(63.2\) m/s

4. \(6.32\) m/s

Subtopic: Â Work Energy Theorem |

Â 66%

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