Best Mechanical Aptitude Test - (Free Mechanical Comprehension Study Guide)

welcome this video tutorial about liquids and hydraulics mechanical comprehension exams often require you to have a basic knowledge of liquids and how their harness in order to produce mechanical systems like hydraulics there are some basic rules of physics that you need to know although these are simplified because tests don't usually require you to know the minut details first liquids are incompressible second liquids always conform to their containers third and in closed liquid when pressure is applied equally distributes that pressure another thing to know is the equation for pressure most simply pressure is equal to force over area for water specifically there's about 0.43 pounds of pressure per square inch for every foot of water depth thus the amount of pressure at the bottom of a 12 foot pool is approximately 5.2 pounds per square inch given the rules above and what we know about pressure let's look at a few examples here is one that displays the basic function of a hydraulic system on one side is a vat of liquid which is connected by a hose to another VAT if the left vat is pressurized to move the liquid down one inch how much will the water level in the other VAT rise assuming they are the same size because of the rules that we mentioned before especially because pressure applied to an enclosed liquid is equally distributed when the liquid on the left that is pressed down one inch the water level on the right VAT will rise exactly one inch another example here are two vets again the left one is half the size of the one on the right in this case if the pump on the Left moves down two inches the one on the right will move up one inch that's because the mechanical advantage is such that only half the force needs to be used on the left but it needs to be pushed twice as far let's try another practice problem imagine a diver is practicing diving in the bottom of a diving pool which has a depth of 20 feet where is the water pressure greatest where the diver is halfway between the bottom and the surface it does not matter because water pressure is always equal the answer is a because water pressure increases by 0.4 three pounds per foot if you remember B is wrong because the surface has almost no pressure relative to the depth of 20 feet C is wrong because water only equally distributes pressure when it's in an enclosed in pressurized space like a hydraulic tube one more practice problem two identical and closed containers of liquid are connected by a pipe if one side receives 12 pounds of force how much will the other side receive due to the connecting pipe a one pound B six pounds C twelve pounds D unknown to answer see because the containers are equal in size and are pressurized so therefore they will distribute weight equally I hope that helps thanks for watching this video tutorial you hi and welcome to this video tutorial on gears on a mechanical aptitude test it's not uncommon to find a couple of questions relating to gears gears are a system of interlocking wheels that can produce massive amounts of mechanical advantage how much mechanical advantage depends on the gear ratio or the relation in size between the gears but before we get too far let's go ahead and take a look at something simple first this is a standard gear question if a spins right be spins left and C spins right which way will D spin there is a very easy trick to determine the answer here if the number of gears is odd it spins the same way as the first a if the number of gears is even the final gear will spend the opposite way of the first make sense problems like these are simple when you know the shortcut closely examine the accompanying image if gear a runs to the right which direction will gear D turn now let's see a more complicated version of the same thing using the same image as a previous question if gear D has twice the diameter of C what is the mechanical advantage of D how many revolutions will see make for every revolution of D there are two questions related to this image so let's take them one at a time first mechanical advantage since we can say gear C is the input gear as it turns the D gear and our input gear is 1/2 the size and has half the number of teeth our mechanical advantage equation is as follows mechanical advantage is equal to the teeth of the output gear over the teeth of the input gear in this case it's 24 over 12 which means we have a mechanical advantage of 2 now let's examine the gear ratio and find how that impacts how much turning these gears will do gear ratio is similar since we know that D has twice as many teeth as C the ratio driving gear to the driven gear is 1 to 2 meaning that for every rotation of C D only revolves 1/2 times make sense now for a couple of fun ones to try by yourself if gear a answer the right which direction will end spin to the right or to the left in this case there's an even number of gears so if we use our simple little cheat it means it's going to go to the opposite direction of the first one in this case to the left last one the smaller gear has 12 teeth and the larger gear has 24 teeth if the smaller gear turns 12 times how many revolutions will the larger gear make the answer here is C because we know the ratio is 1 or 2 which means the larger gear makes half as many turns as a smaller one half of 12 turns is 6 I hope that helps thanks for watching this video tutorial fine welcome to this video tutorial on horsepower knowing a little bit about horsepower can be incredibly helpful in a mechanical comprehension exam there are multiple ways of defining one horsepower all of which are REITs the most commonly used terms are electrical and mechanical horsepower first electrical horsepower refers to an amount of joules created per second instead of saying joules per second however we can simply say watt or watts one electrical horsepower is 746 watts or joules expended per second for mechanical horsepower we're talking about how much force it will take to move one pound one foot over a period of one second it is often agreed that one mechanical horsepower can do five hundred foot-pounds per second of work or 33 thousand foot-pounds per minute with that knowledge in mind let's go ahead and try a couple of practice problems first something really easy the power needed to move five hundred fifty pounds one foot over a period of one second is commonly referred to as what a a Joule be a watt see a torque or D horsepower obviously the answer in this case is d one horsepower now let's take a look at something a little bit more realistic closer to something you'll see on the test Jack needs to pull a truck for one minute the truck weighs 115 point five tons what's the minimum number of horsepower necessary to accomplish this a three horsepower B seven horsepower C 21 horsepower or D 420 horsepower the answer is B seven here's how we got the answer first we multiply the number of tonnes by 2,000 pounds this will give us the weight of the truck in pounds once we have that we divide by one horsepower or rather the work that can be accomplished by one horsepower which is 33 thousand foot-pounds per minute so having done that we seven an elevator motor requires five thousand nine hundred sixty eight watts to move the elevator what is the horsepower of the electric motor operating the elevator a 7 B 8 C 13 or D 746 to find our answer all we have to do is divide the number of watts produced by the motor by the number of watts that we know a horsepower can produce 746 that leaves us with the answer 8 B I hope that helps thanks for watching this video tutorial I welcome this video tutorial about power friction and efficiency we know that whenever we work forces act against this for example when I try to push a box across a floor there's this thing called friction that makes it more difficult than simply pushing the weight of the box because I'm pushing the weight of the box and the resistance of friction and when the weight of the Box increases so can friction this means I'm not as efficient as I could be the same is true for engines and other things that's why we add oil and lubricants to make the friction decrease in our efficiency increase sometimes questions about friction and efficiency end up on our mechanical comprehension exams so let's be ready and try a couple of practice problems imagine you're using a pulley system to lift the box that weighs 100 pounds but the pulleys are only 50% efficient how many pounds of force are you actually putting into moving the box here's how to solve one of these just divide power output by efficiency here our power output is 100 an efficiency is 0.5 0 or 50% thus power output divided by efficiency is equal to 100 over 0.5 and now we know our initial force which is 200 pounds make sense here's one to try by yourself an engine produces 90 horsepower and is 90% efficient so how much horsepower is being lost because of inefficiency remember the output is placed over the efficiency 90 horsepower over 0.9 in this case that's equal to 100 horsepower and that is what the engine would be on total efficiency but the question is asking how much is being lost due to inefficiency so we subtract 90 horsepower output from the 100 horsepower which would be the 100 percent efficiency and we end up with 10 horsepower 10 horsepower is being lost due to inefficiency I hope that helps thanks for watching this video tutorial hi welcome to this video tutorial on on pulleys McElveen comprehension tests often address pulleys so it's important to understand their advantages and how they work first let's start with a simple fixed pulley system a fixed pulley is when a rope or chain or something similar is wrap around a wheel or axle in order to raise removal weight like this in this case the wheel or axle simply changes the direction of the force exerted to move the weight this all changes when a double pulley or block-and-tackle system is used when multiple pulleys are used their mechanical advantages increase and the weight becomes easier to move here we have a block and tackle or movable pulley system one pulley is still fixed in this case to the ceiling while the other moves with the object itself here we can see the force exerted by someone pulling with 50 Newtons that force goes around the pulley and acts on the weight but then it goes around the second pulley once again acting upon the weight that original 50 Newton's of force acts towards raising the weight every time it circles the pulley this provides a significant advantage as you can see here since the person pulling can raise a hundred Newton weight with only 50 Newton's of force of course in these examples in likely many of the problems you will see friction is neglected this all means that a 4-legged pulley system is equal to four times the original force exerted to move the weight mechanical advantage of a four legged pulley system is equal to four times the original force exerted to lift the weight the equation and find out how many times the rope should wrap between the fixed block pulley and the movable pulley is the same equation used to find the mechanical advantage here ma equals mechanical advantage W equals weight t is equal to tension or the force to use the pole an N equals a number of legs or times the rope travels between the two pulleys let's try an example problem the man on the right is trying to lift this large package the package weighs 200 pounds how much force does the man have to exert in order to move the package upward I'll give you a moment to try to figure out by yourself you here's the answer first let's take a look at the mechanical advantage for this pulley system using our equation it looks like we have a mechanical advantage of 2 because in this case n is equal to 2 so that means the force of the man's pole will be doubled yet even that won't be enough to lift the 200-pound package in this case the answer is no the man will not be able to lift the weight even if he pulls with 80 pounds of force I hope that helps thanks for watching this video story hi welcome this video tutorial about levers levers are the most commonplace of all the simple machines from shovels and knives to wheelbarrows and baseball bats levers are everywhere we look there are several components that every lever has so let's go over and review those every lever must have a fulcrum a point at which elaborate AIT's a resistance the force acting against the effort applied and obviously the application of effort to move the lever there are three classes of levers they are differentiated by the positioning of the fulcrum resistance and application of effort in a first class lever the fulcrum is between the effort and the resistance a seesaw is a good example of a first class lever when effort is applied to force one into the lever upward the end where the force is applied must go down like a seesaw the shorter the distance between the fulcrum and the resistance the easier it will be to move this is a result of the mechanical advantage but we'll get to that later second class levers is where the resistance is in between the fulcrum and the effort whereas a first class lever is able to increase force and distance through mechanical advantage a second class lever is only able to increase force a common example of a second class lever is the wrench the force exerted by your hand at one end of the wrench is magnified at the other end basically with the second class lever you're producing greater force at the other end in a third class lever the force is applied in between the fulcrum and the resistance a baseball bat is a classic example of the third class lever the end of the bat where the ball is struck is the resistance by exerting the effort at the base of the bat close to the fulcrum you are able to make the end of the bat fly quickly through the air now that we've defined all three classes of levers I'm going to show you a series of images now I want you to identify each one of these images as a certain type of lever let's get started with this first image what is it first second or third class lever that's right second class lever because the resistance is in between the fulcrum in the effort here's another image to identify this is a third class lever look at where the force is applied it's in between the fulcrum and the resistance like a baseball bat this is a third class lever I hope that helps thanks for watching this video tutorial hi welcome this video tutorial about wedges now wedges are one of the most common simple machines as they don't have any moving parts but provide a large mechanical advantage as you are aware the shape of wedge is just triangle usually isosceles so that the lengths of two sides are equal like the example shown here sometimes objects called inclined planes are also used to the same effect thankfully finding the mechanical advantage of these two objects is relatively easy take for example this wedge it has a length of 10 units in a width of 4 units the equation for finding mechanical advantage is M a is equal to L over W where L is equal to length and W is equal to width so in this case we divide 10 by 4 which equals 2.5 the mechanical advantage is 2.5 let's try another in this example we have a wedge that has a length of 21 units and a width of 3 what's the mechanical advantage of this wedge well as you can see it's just going to be 7 because we divide the length 21 by the width which is only 3 make sense try a couple on your own a wedge is 14 inches in length and the mechanical advantage is 7 what is the width of the tool we already know that the mechanical advantage is 7 and we know that the length is 14 we're dividing 14 by something to get seven dancers 2 now if you're concerned about inclined planes don't be like I said they work almost exactly the same as a wedge the mechanical advantage is similarly calculated as well so here's an example the length is 15 height is five the mechanical advantage is 315 divided by 5 is 3 let's try one more practice problem a truck ramp is used for its mechanical advantage if it's 18 meters long and 3 meters high what is the mechanical advantage of this inclined plane the answer is 6 18 divided by 3 is 6 I hope that helps thanks for watching this video tutorial you hi welcome to video tutorial on work in science we say enforce accomplishes work when there is a displacement at the point of application of that force in the direction of that force now if none of that made sense to you don't worry I'm going to explain the unit of measurement of work is the Joule which is the force expended in Newton's times the distance traveled in meters so for example imagine there is a box in the ground you go to lift it one meter off the ground if you cannot get it off the floor you have not achieved work if however you do lift it one meter and expend 20 Newton's of energy doing so you have achieved 20 joules of work because you lift in the Box one meter using 20 Newtons and 20 Newton's times one meter is 20 joules make sense let's try some other examples if a rock-climber expands 660 Newtons up a 30 meter cliff how much work did he exert the answer is d 19,800 joules because we multiply 616 UNS by 30 meters let's try another one a child uses three and a half Newton's to throw a ball into the air about 2.3 meters how much work has she achieved the answer is C 8.05 joules again we only have to multiply 3.5 Newton's by 2.3 meters so as long as we remember that work is always going to be defined in terms of force expanded to displace a body over distance we will get the right units usually joules to find our answer we simply multiply the force by the distance usually Newton's times meters make sense I hope that helps thanks for watching this video tutorial

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Keywords: Mechanical Aptitude, Mechanical Comprehension, Mechanical Aptitude Test, Mechanical Comprehension Test, Mometrix Test Preparation, Mechanical Aptitude Study Guide, mechanical comprehension, mechanical aptitude test, asvab, free mechanical aptitude test, free online mechanical aptitude test, mechanical aptitude test questions, mechanical aptitude study guide, mechanical aptitude tests, mechanical comprehension test, mechanical reasoning, mechanical aptitude

Id: nvH06GcLeMI

Length: 22min 36sec (1356 seconds)

Published: Mon Nov 02 2015