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Mechanical aptitude tests measure your knowledge of straightforward mechanical concepts including: levers, pulleys, gears, springs, simple electrical circuits and tools. If you are taking a mechanical aptitude test for the emergency services or the military then the questions will tend to concentrate on principles rather than on making calculations. For example, you may be shown diagrams of a lever and asked which one is the most efficient. If you are taking a test for a craft or apprenticeship job, then you can expect some questions involving calculations.

A lever consists of a bar which pivots at a fixed point known as the fulcrum. In the example shown the fulcrum is at the center of the lever. This lever provides no mechanical advantage and the force needed to lift the weight is equal to the weight itself.

However, if you want to lift a weight that is heavier than the force applied you can move the fulcrum closer to the weight to be lifted. This affects the force required in the following way:

                                                w x d1 = f x d2

In this example the fulcrum has been moved towards the weight so that the weight is 1 meter from the fulcrum. This means that the force can now be applied 2 meters from the fulcrum.

If you needed to calculate the force needed to lift the weight then you can rearrange the formula.

                             w x d1 = f x d2     can be rearranged to     f = (w x d1)/d2

                        f = (10 x 1)/2    (10/2 is the same as 5/1, the force required is 5 Kg)

Example Question
How much force is required to lift the weight?

          A) 40lbs          B) 50lbs          C) 60lbs          D)70lbs

Answer
C - 60lbs is needed to lift the weight. It can be calculated like this:

                                     f = (w x d1)/d2
                                     f = (80 x 9)/12
                                     f = (720)/12
                                     f = 60 lbs

In practice, levers are used to reduce the force needed to move an object, in other words to make the task easier. However, in mechanical aptitude questions it is possible that you will see questions where the fulcrum has been placed closer to the force then the weight. This will mean that a force greater than the weight will be required to lift it.

You may see more complex questions involving levers, where there is more than one weight for example. In this case you need to work out the force required to lift each weight independently and then add them together to get the total force required.

The pulleys used in this type of question are made up a grooved wheel and a block which holds it. A rope runs in the groove around the wheel and one end will usually be attached to either: a weight, a fixed object like the ceiling or to another pulley. For the purposes of these questions you can ignore the effect of friction.

Single Pulley
Which weight requires the least force to move?

A) A              B) B           C) Both require the same force

Answer
B – Weight B requires a force equal to 5 Kg whereas A requires a force equal to 10 Kg.

Single pulley questions are relatively straightforward. If the pulley is fixed, then the force required is equal to the weight. If the pulley moves with the weight then the force is equal to half of the weight. Another way of thinking about this is to divide the weight by the number of sections of rope supporting it to obtain the force needed to lift it. In A there is only one section of rope supporting the weight, so 10/1 = 10 Kg required to lift the weight. In B there are two sections of rope supporting the weight, so 10/2 = 5 Kg required to lift it.

Double Pulleys
There are two possible ways that two pulleys can be used. Either one pulley can be attached to the weight or neither of them can be.

Which weight requires the least force to move?

A) A              B) B           C) Both require the same force

Answer
A – Weight A requires a force equal to 5 Kg whereas weight B requires a force equal to 10 Kg. Remember to divide the weight by the number of sections of rope supporting it to get the force needed to lift the weight.

Using More Than Two Pulleys
How much force is required to move the weight?

A) 100 Kg       B) 150 Kg        C) 50 Kg         D) 60 Kg

Answer
C – The weight is 300 Kg and there are 6 sections of rope supporting it. Divide 300 by 6 to get 50 Kg. In all cases, just divide the weight by the number of sections of rope supporting it to get the force needed to lift the weight.

A gear is a toothed wheel or cylinder that meshes with another toothed component to transmit motion or to change speed or direction. Gears are attached to a rotating shaft turned by an external force, which is not usually illustrated in these types of question. Two gears may be connected by touching each other directly or by means of a chain or belt.

If gears are connected by a chain or belt then they move in the same direction.

If the gears are touching (meshed) then adjacent gears move in opposite directions. In this example the first and third gear will turn in the same direction. When there are an odd number of meshed gears then the last gear will always turn in the same direction as the first one.

Meshed gears with an equal number of teeth will turn at the same speed. If they have an unequal number of teeth then the gear with the fewest teeth will turn faster. To work out how fast one is turning with respect to the other you need to count the teeth.

A spring is piece of wire or metal that can be extended or compressed by an external force but which then returns to its original length when that force is no longer applied.

There are many different types of spring including, spiral coil, leaf springs and torsion springs. Springs are used in many applications including clocks, vehicle suspensions etc. In the type of questions that you will be asked in mechanical aptitude tests, you can assume that springs behave in a linear way. That is, doubling the force applied will stretch or compress the spring twice as much.

Springs in Series & Parallel
If more than one spring is used then they can be arranged in one of two ways, either in series or in parallel.

When springs are arranged in series, each spring is subjected to the force applied. When the springs are arranged in parallel the force is divided equally between the springs.

Questions on electricity usually take the form of simple circuit diagrams.

These diagrams are usually restricted to showing the power source, switches, loads (typically bulbs), and the path of the wiring. To answer these questions you need a basic understanding of how electricity flows around a circuit.

The ability to approach a maintenance or repair problem in a logical and systematic way to to locate the fault is critical when working with complicated systems like those found in aircraft, ships and communications equipment.

Example Fault Diagnosis Question

There are two components to this question.

1. A grid which describes the function of a series of switches.
2. A flowchart showing: input – switches – output.

Each of the switches acts to alter the input before the next switch in the series.

This grid shows four switches and their effect on four numbered inputs which may be either on or off. The first switch (diamond symbol) inverts inputs one and two. That is, if the input is on, it is turned off and if it is off it is turned on. The other switches act in a similar way as detailed in the grid. If a switch is not working then it has no effect on the input which passes through unchanged.

In this example flowchart, all of the inputs (numbered 1, 2, 3, 4) are on.
When these inputs pass through the first switch 1 & 3 are inverted (i.e. switched off).
These modified inputs (1=off, 2=on, 3=off, 4=on) then pass through the second switch.
The second switch inverts inputs 3 & 4, which gives (1=off, 2=on, 3=on, 4=off).
These modified inputs (1=off, 2=on, 3=on, 4=off) then pass through the third switch.
The third switch should invert inputs 2 & 4, giving (1=off, 2=off, 3=on, 4=on).

However the third switch is not working so the output from switch two is not changed.
The answer to this question is therefore ‘C’ – because switch type ‘C’ is at fault.

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Buy Now - Immediate Download   This 235 page eBook will show you how to increase your speed and accuracy in mechanical aptitude tests. It contains examples and explanations covering every type of question you are likely to encounter including; levers, pulleys, gears, springs, tools, workshop arithmetic, fault diagnosis, spatial ability, abstract reasoning and math questions.   This eBook is in Letter/A4 format for easy printing and self marking. It contains 750 practice questions split into 28 tests.   Only $19 (235 pages)   Don't forget to click 'Return to Merchant' on PayPal payment page.