Mechanical comprehension tests are widely used during selection processes that involve technical jobs. Having an understanding of mechanical advantage is crucial to your success during the test. You may find that some mechanical comprehension tests ask you to calculate the mechanical advantage of a simple pulley system.
WHAT IS MECHANICAL ADVANTAGE?
Mechanical advantage is quite a simple concept. Essentially, it is the advantage gained when using some kind of machinery, such as a lever, fulcrum, or pulley, to exert force. In other words, it’s how much the piece of equipment helps you to move an object by minimising the amount of force that you need to put into it.
EXAMPLES OF SIMPLE PULLEY SYSTEMS
Here’s an explanation of how mechanical advantage works when using a simple pulley system.
If you study the three pulley systems above you will note that each system has both supporting ropes and non-supporting ropes. Supporting ropes are ones which, as the name suggests, support the load. Only the first two pulley systems have non-supporting ropes which I have indicated. The non-supporting ropes in the first two pulley systems above simply change the direction of the force.
To calculate the mechanical advantage in a moveable pulley system, we simply have to count the number of supporting ropes. Counting the supporting ropes in the pulley systems above, the mechanical advantage of each of system is, from left to right 2, 3, and 5.
In order to demonstrate further the concept of mechanical advantage using simple pulley systems, please try the following sample two questions to see how you get on.
Question 1 – What is the Mechanical Advantage?
Question 2 – What is the Mechanical Advantage?
In question 2 you will notice that the pulley is not attached directly to the beam. This is known as a moveable pulley system whereby the pulley is attached to the load/weight. When the rope is pulled up the weight/load will also move up. You will notice that the weight is supported by both the rope end attached to the upper beam and the end which will be held by the person.
Each side of the rope is now supporting the weight; therefore, each side carries only half the weight. The advantage of this system is 2.
You should now have a good idea about how to deal with mechanical reasoning questions which require you to understand theoretical mechanical advantage. Before you sit any mechanical comprehension test make sure you gain a full understanding of pulley systems, cogs and levels. We recommend you obtain our informative and detailed book on this type of test, How to Pass Mechanical Comprehension Tests.