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RopeLab Quiz 1: Mechanical Advantage

Richard Delaney August 26, 2019 Free content, Quick Quizzes 4 Comments

This quiz presents 10 short questions from the Mechanical Advantage content presented in the one-day RopeLab: Physics for Roping Technicians workshop.  It tests your theoretical understanding of Mechanical Advantage in a range of simple scenarios.

Although there are many ways to discuss and calculate Mechanical Advantage, the following terms are used in this quiz:

  • Ideal Mechanical Advantage (IMA): the best possible MA for a system ignoring any friction, stretch, and imperfect angles.
  • Theoretical Mechanical Advantage (TMA): the best guess at MA taking friction into account for each change in direction (pulleys, carabiners, edges, etc).

Actual Mechanical Advantage (AMA) refers to the MA measured in the system once built and tested.

All of the images in this quiz have been created using vRigger (http://vrigger.com).

© Richard Delaney, RopeLab 2015.

1. 

This image shows an operator standing on the ground attempting to raise a his partner. What is the Ideal Mechanical Advantage of this system (ignore friction)?

2. 

This image shows an operator attempting to raise himself by pulling down on the yellow rope. What is the Ideal Mechanical Advantage (ignoring friction) of this system?

3. 

This image shows an operator attempting to raise their partner by pulling down on the yellow rope.  What is the Ideal Mechanical Advantage (ignoring friction) of this system?

4. 

This image shows an operator attempting to raise themselves by pulling down on the yellow rope.  What is the Ideal Mechanical Advantage (ignoring friction) of this system?

5. 

This vehicle is attempting to move itself by taking in rope on the front mounted winch.  What is the Ideal Mechanical Advantage (ignoring friction) of this system?

6. 

This vehicle is attempting to move itself by taking in rope on the front mounted winch.  What is the Ideal Mechanical Advantage (ignoring friction) of this system?

7. 

This vehicle is attempting to move itself by taking in the grey rope on the front powered mounted winch.  What is the Ideal Mechanical Advantage (ignoring friction) of this system?

8. 

The image shows a scenario where a person is being held in place by a rope supported by an overhead anchor.  What is the theoretical magnitude of the force on Anchor A?

9. 

The image shows a scenario where a person is being lowered by a rope supported by an overhead anchor.  What is the theoretical (including friction) magnitude of the force on Anchor B?

10. 

This image shows a scenario where a person is being lowered by a rope supported by an overhead anchor.  What is the theoretical (including friction) magnitude of the force on Anchor C?

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About The Author

Richard Delaney

Richard Delaney has worked professionally with ropes since 1992 as a multi-pitch rock-climbing instructor, technical rescue instructor and rope access technician. Understanding and teaching the Physics of Rigging is a core passion of Richard’s, one based on his experience, and his prior professional life as a qualified engineer.

4 Comments
  1. Jay Zhang
    September 23, 2019 |

    In scenario 3 and 4, if only one of the pulleys was inefficient, does it matter where in the system it is placed? My initial thought is that it shouldn’t matter, but it also feels like a case where it surprisingly might. In general, should inefficient pulleys be close to the load or the hauler? Or again, does it not matter?

    • Richard Delaney
      September 23, 2019 |

      As a general rule, place the most efficient pulley closest to the hauler as that preserves the most force forwards through the system. An exception to this is ‘drop loop’ type systems where we place a pulley on the load. This effectively halves the weight of the load.

  2. brightj
    May 18, 2021 |

    How could the car move backwards if the rope is being winched into the front of it? The rope is already taut, and there is no slack to take up. It would have a force pulling the rear bumper off the back of the car and a force pulling the winch off the front of the car. Are you assuming that the rope stretches?

  3. Richard Delaney
    May 18, 2021 |

    Have a look at this video:
    https://youtu.be/aYNxJJd6fCA

    I made this to answer the reverse winch question.

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