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ASVAB · Mechanical Comprehension · Topic Study Guide

Simple Machines (Levers, Pulleys, Gears): Practice Questions & Explanations

23 Mechanical Comprehension questions on simple machines (levers, pulleys, gears), each with a worked explanation citing the source handbook.

Source: Official ASVAB content outline (Mechanical Comprehension subtest) covering simple machines, mechanical motion, structural support, and basic fluid dynamics.

Reviewed by Jordan Morley, Editorial Lead at 247SimpleTests. Written by the 247SimpleTests Editorial Team from the official source material cited on every question.

Why this topic matters

Simple machines — levers, pulleys, gears, inclined planes, wheel-and-axle, screws — are the heart of Mechanical Comprehension. Each question comes down to mechanical advantage: how much the machine multiplies force, and the trade-off in distance.

Below are every simple machines (levers, pulleys, gears) question in our Mechanical Comprehension bank. Read each question, try to answer before reading the explanation, and use the source citations to look up anything you want to verify.

1. A first-class lever has the fulcrum located:
  1. A At one end with the load at the other
  2. B Not at all — first-class levers have no fulcrum
  3. C Between the effort (force applied) and the load (resistance)
  4. D Between the load and the end of the lever

Explanation

Three classes of levers, distinguished by the positions of fulcrum, effort, and load: (1) FIRST-CLASS: fulcrum is BETWEEN effort and load. Examples: seesaw, scissors, crowbar, pliers, claw hammer pulling nails. Effort and load move in opposite directions. Mechanical advantage can be >1, =1, or <1 depending on lengths. (2) SECOND-CLASS: load is BETWEEN fulcrum and effort. Examples: wheelbarrow, nutcracker, bottle opener, door (hinge=fulcrum, doorknob=effort, weight=load). Always provides mechanical advantage >1 (force multiplier). Effort and load move same direction. (3) THIRD-CLASS: effort is BETWEEN fulcrum and load. Examples: tweezers, fishing rod, broom, human forearm (elbow=fulcrum, biceps=effort, hand/load = third class). Always has mechanical advantage <1 (speed multiplier — gives distance/speed at cost of force). Effort and load move same direction. Mnemonic 'F-L-E' for what's in the MIDDLE: First class = Fulcrum middle; second class = Load middle; third class = Effort middle. Mechanical advantage = effort arm length ÷ load arm length. ASVAB MC frequently asks identification and MA calculation.
Source: ASVAB MC, Levers

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2. A fixed (single) pulley provides what mechanical advantage?
  1. A 2
  2. B 1 — it changes the direction of force but does not multiply it
  3. C 0
  4. D 4

Explanation

Pulley mechanical advantage equals the number of rope segments supporting the load. (1) FIXED PULLEY (single, attached to a fixed point): MA = 1. It changes direction (pulling down to lift up) but does not reduce the force needed. The load and effort move equal distances. Example: a flag-raising pulley. (2) MOVABLE PULLEY (attached to the load itself): MA = 2. Two rope segments support the load, halving the effort needed, but doubling the distance the rope is pulled. (3) COMPOUND PULLEY SYSTEMS (block and tackle): MA = number of supporting rope segments. A 4-pulley system with 4 supporting segments has MA = 4 — one-quarter the force, four times the distance. Trade-off principle (universal in simple machines): mechanical advantage = force multiplied / distance reduced. Force × Distance = Work; ignoring friction, work in = work out. A 4:1 pulley needs 1/4 the force but pulls 4 times the rope. Real-world losses to friction reduce ideal MA. Counting supporting segments: count the rope segments under the movable pulley(s) that actually support the load, not the rope you're pulling on (which is on top). For typical ASVAB problems, draw the system and count.
Source: ASVAB MC, Pulleys

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3. If gear A has 20 teeth and meshes with gear B that has 60 teeth, when gear A makes 6 full rotations, how many rotations does gear B make?
  1. A 2
  2. B 6
  3. C 18
  4. D 60

Explanation

Gear ratio = (teeth of driven gear) / (teeth of driver gear) = 60/20 = 3:1. When a smaller gear drives a larger gear, the larger gear rotates SLOWER but with more torque. Calculation: gear A (20 teeth, 6 rotations) — total teeth moved = 20 × 6 = 120 teeth. Gear B has 60 teeth, so 120 / 60 = 2 rotations. General principle: teeth pass at the same rate where gears mesh. Rotations of A × teeth of A = rotations of B × teeth of B. Gear systems: (1) SMALL driving LARGE: torque multiplied, speed reduced (used to lift heavy loads slowly); (2) LARGE driving SMALL: speed multiplied, torque reduced (used in bicycles for fast pedaling at high gear); (3) DIRECTION: meshing gears rotate in OPPOSITE directions; an idler gear between them keeps them rotating in the same direction; chain or belt drives between gears keep them rotating in the SAME direction. Gear trains: multiple gears in series — overall ratio is product of individual ratios. Bicycle gears: smaller front × larger back = easier pedaling (climbing); larger front × smaller back = faster speeds (flat ground). Common ASVAB MC questions: gear ratios, rotation counts, rotation direction, torque multiplication.
Source: ASVAB MC, Gears

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4. A screw with 10 threads per inch is used to lift a heavy load. If the handle is turned through one full revolution, how far does the screw advance into the material?
  1. A 1/2 inch
  2. B 1 inch
  3. C 1/10 inch (0.1 inch)
  4. D 10 inches

Explanation

Screw pitch = distance the screw advances per revolution = 1 / (threads per inch). 10 threads per inch → pitch = 1/10 = 0.1 inch per revolution. A screw is essentially an inclined plane wrapped around a cylinder. Mechanical advantage of a screw = (2π × radius of handle/screw) / pitch. Example: a screw with 10 threads per inch and a wrench handle 6 inches from center: MA = (2π × 6) / 0.1 = 37.7 / 0.1 = 377. The operator pushes the wrench around a 37.7-inch circumference to advance the screw 0.1 inch — huge force multiplication. This is why screws and wedges can split logs, lift cars (jacks), and clamp materials with relatively modest applied force. Bolts and nuts use the same principle. Screws come in many designs: machine screws (uniform threads for nuts), wood screws (tapered for wood), self-tapping screws (cut their own threads), sheet metal screws, etc. Wedges: similar inclined-plane concept used to split or hold (axes, chisels, doorstops). Combined simple machines: most real-world devices use combinations — a bicycle has wheels and axles, gears (modified wheels), levers (pedals and crank arms), and pulleys (chain drive). Car jacks combine a screw with a lever (the handle). Practical ASVAB MC scenarios test recognizing screws in tools and calculating advancement per rotation.
Source: ASVAB MC, Screws

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5. A wheel and axle has a wheel with a radius of 12 inches and an axle with a radius of 3 inches. If a force of 25 lbs is applied to the wheel, what force is exerted at the axle?
  1. A 100 lbs
  2. B 300 lbs
  3. C 6.25 lbs
  4. D 25 lbs

Explanation

Wheel and axle is a simple machine where two cylinders of different radii are fixed together and rotate together. Mechanical advantage = radius of wheel / radius of axle = 12/3 = 4. Force at axle = 25 × 4 = 100 lbs. The wheel (larger radius) gets the input force; the axle (smaller radius) outputs the higher force. Trade-off: the axle moves a shorter distance — if the wheel rotates once and covers 2π(12) ≈ 75 inches at its edge, the axle rotates once and covers 2π(3) ≈ 19 inches. The same work (Force × Distance) is done by both. Wheel and axle applications: (1) STEERING WHEEL — large wheel turns steering column (axle) — force multiplier; (2) SCREWDRIVER — handle is the wheel, shaft is the axle — force multiplier for turning screws; (3) DOORKNOB — knob is wheel, latch mechanism is axle; (4) PENCIL SHARPENER — handle is wheel; (5) WINDLASS — well winch, anchor windlass; (6) FAUCET HANDLE — handle is wheel, valve stem is axle. Reverse application (speed multiplier instead of force multiplier): bicycle wheel — pedals/crank apply force at small radius (the axle), wheel rim (large radius) moves faster but with less force per unit of pedal force. Gears connecting wheels and axles transmit power efficiently in machines. The lever family (lever, wheel/axle, pulley) all share the principle of trading force for distance through rotational geometry.
Source: ASVAB MC, Wheel and Axle

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6. Which of the following is NOT one of the six classical simple machines?
  1. A Screw
  2. B Battery
  3. C Lever
  4. D Wedge

Explanation

The six classical simple machines (Renaissance scientists, building on ancient Greek engineering): (1) LEVER — rigid bar pivoting on a fulcrum; (2) WHEEL AND AXLE — two cylinders of different radii fixed together; (3) PULLEY — wheel with a grooved rim for a rope or cable; (4) INCLINED PLANE — sloped surface; (5) WEDGE — two inclined planes back-to-back, used to split (axes, chisels) or hold (doorstops, nails); (6) SCREW — inclined plane wrapped around a cylinder. A battery is not a simple machine — it's an electrochemical device that stores and provides electrical energy. Simple machines change the direction or magnitude of mechanical force; they don't create energy, only transform mechanical advantage. All complex machines are combinations of simple machines: (1) BICYCLE — wheel and axle (wheels), levers (pedals, crank, handlebars), pulleys/chain (gear system), wedges (rim brakes); (2) SCISSORS — two first-class levers sharing a fulcrum; (3) CAN OPENER — lever (handles), wheel and axle (turning mechanism), wedge (cutting blade); (4) WHEELBARROW — second-class lever; (5) CAR JACK — screw and lever; (6) CRANE — pulleys, levers, wheels. The principles of work, energy, and mechanical advantage learned through simple machines apply to all mechanical systems. ASVAB MC questions on simple machines test identification, calculation of mechanical advantage, and application to real tools.
Source: ASVAB MC, Simple Machines Overview

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7. Two gears mesh together. Gear A rotates clockwise. Which direction does gear B rotate?
  1. A Counterclockwise (opposite direction)
  2. B It depends on the size of the gears
  3. C Both directions simultaneously
  4. D Also clockwise

Explanation

MESHING gears rotate in OPPOSITE directions. Their teeth interlock at the contact point; as one gear pushes its tooth into the other, that contact point on each gear must move in the same linear direction at that instant — but since they're rotating around different axes, this means opposite rotational directions. Common in: car transmissions (gears alternate direction); clock mechanisms; rotating machinery. To keep two gears rotating in the SAME direction, an IDLER GEAR can be placed between them. The idler reverses direction once (from the driver), then reverses again (to the driven gear), resulting in net same direction. Idlers don't change the gear ratio (their teeth count cancels out) but they: (1) Change rotation direction; (2) Bridge a gap between gears that can't mesh directly; (3) Take up slack or stress in chain drives. CHAIN/BELT drives connect gears (sprockets/pulleys) and keep them rotating in the SAME direction (the chain only goes one way around its loop). REVERSED belts (crossed) make them rotate opposite — used in old machinery but uncommon today.

Planetary gear systems: sun gear in center, planet gears around it, ring gear around them; complex rotation relationships; used in automotive automatic transmissions and many other applications.

Rack and pinion: a circular pinion gear meshes with a straight rack; converts rotation to linear motion (or vice versa); used in steering systems (turn wheel rotates pinion which slides rack linking to wheels), elevators, machine tools. ASVAB MC commonly tests gear direction prediction in gear trains.

Source: ASVAB MC, Gear Direction

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8. A lever has a 6-foot effort arm and a 2-foot load arm. What is the mechanical advantage?
  1. A 4
  2. B 1
  3. C 2
  4. D 3

Explanation

MA (lever) = effort arm ÷ load arm = 6 ÷ 2 = 3. A mechanical advantage of 3 means 1 pound of effort lifts 3 pounds of load.
Source: ASVAB MC, Levers

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9. A small gear with 10 teeth drives a large gear with 40 teeth. If the small gear rotates at 200 RPM, what is the large gear's speed?
  1. A 50 RPM
  2. B 800 RPM
  3. C 100 RPM
  4. D 25 RPM

Explanation

Gear ratio = driver teeth / driven teeth = 10/40 = 1/4. Large gear speed = 200 × (10/40) = 200 × 0.25 = 50 RPM. When a small gear drives a larger one, the larger gear turns more slowly but with more torque — speed and tooth count are inversely related. Each turn of the 10-tooth gear advances the 40-tooth gear by only a quarter turn, so 200 RPM becomes 50 RPM. The distractor 800 RPM applies the ratio backwards (that would be the result if the 40-tooth gear were driving), 100 RPM halves instead of quartering, and 25 RPM uses a ratio of 1/8.
Source: ASVAB MC, Gears

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10. A wheel-and-axle system has a wheel radius of 12 inches and an axle radius of 3 inches. What is the mechanical advantage?
  1. A 2
  2. B 4
  3. C 36
  4. D 3

Explanation

MA (wheel and axle) = wheel radius ÷ axle radius = 12 ÷ 3 = 4. A wheel and axle is a rotating lever: the wheel radius is the effort arm and the axle radius is the load arm, so the mechanical advantage is their ratio. A force applied at the rim of the 12-inch wheel is multiplied four times at the 3-inch axle (think of a steering wheel or a screwdriver handle). The distractor 36 multiplies the radii, 3 is the axle radius alone, and 2 would need a 6-inch wheel.
Source: ASVAB MC, Wheel and Axle

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11. A screw has 30 threads per inch. How far does it advance into a material when turned 3 full rotations?
  1. A 3 inches
  2. B 0.30 inches
  3. C 0.05 inches
  4. D 0.10 inches

Explanation

Screw pitch: 30 threads per inch means each full rotation advances the screw 1/30 inch. 3 rotations × (1/30 inch per rotation) = 3/30 = 0.10 inches. The screw is a simple machine (inclined plane wrapped around a cylinder) that converts rotational force (torque) into linear force and motion. MORE THREADS PER INCH = finer pitch = more mechanical advantage per turn = less advance per turn. FEWER THREADS PER INCH = coarser pitch = less mechanical advantage = more advance per turn.

Source: ASVAB MC, Screw — Thread Advance

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12. In a first-class lever (like a seesaw), where is the fulcrum located?
  1. A Between the effort (force) and the load
  2. B At the load
  3. C There is no fulcrum
  4. D At one end

Explanation

In a FIRST-CLASS LEVER, the FULCRUM is located BETWEEN the effort (applied force) and the load — like a seesaw or a pair of scissors. ASVAB Mechanical Comprehension tests the three classes of levers:

First-class: fulcrum in the middle (seesaw, crowbar, scissors).

Second-class: load in the middle (wheelbarrow, nutcracker).

Third-class: effort in the middle (tweezers, human forearm). Levers provide mechanical advantage. Knowing the arrangement (what's in the middle) for each lever class is commonly tested.

Source: ASVAB Mechanical Comprehension — Levers

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13. Two meshed gears turn in what directions relative to each other?
  1. A Both stop
  2. B The same direction
  3. C Random directions
  4. D Opposite directions

Explanation

Two directly MESHED (interlocking) gears turn in OPPOSITE directions — if one turns clockwise, the other turns counterclockwise. ASVAB Mechanical Comprehension tests gear systems.

Gear direction: adjacent meshed gears always rotate oppositely.

Gear ratio/speed: a smaller gear driving a larger gear turns the larger one SLOWER but with more torque; a larger gear driving a smaller one turns it FASTER with less torque. To make two gears turn the SAME direction, you add a third (idler) gear between them. Gear direction and speed relationships are commonly tested.

Source: ASVAB Mechanical Comprehension — Gears

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14. What is the main advantage of using a system of multiple pulleys?
  1. A It reduces the amount of force needed to lift a load (provides mechanical advantage)
  2. B It speeds up the lift only
  3. C It has no effect
  4. D It makes the load heavier

Explanation

A system of MULTIPLE PULLEYS reduces the FORCE needed to lift a load by providing MECHANICAL ADVANTAGE. ASVAB Mechanical Comprehension tests pulleys. A single fixed pulley just changes the direction of force (no force reduction). Adding movable pulleys (a block and tackle) reduces the force needed — but you must pull the rope a greater distance (trade-off: less force over more distance). The mechanical advantage roughly equals the number of rope segments supporting the load. Understanding that pulleys reduce required force is commonly tested.
Source: ASVAB Mechanical Comprehension — Pulleys

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15. An inclined plane (ramp) makes lifting a heavy object easier by:
  1. A Making the object lighter
  2. B Eliminating the need for force
  3. C Increasing gravity
  4. D Reducing the force needed by increasing the distance over which the force is applied

Explanation

An INCLINED PLANE (ramp) reduces the FORCE needed to raise an object by spreading the work over a greater DISTANCE. ASVAB Mechanical Comprehension tests simple machines. Instead of lifting straight up (high force, short distance), you push up the ramp (less force, longer distance) — the work (force × distance) is about the same, but the force is reduced. A LONGER, more gradual ramp requires less force than a short, steep one. This force-distance trade-off (mechanical advantage) applies to all simple machines and is commonly tested.
Source: ASVAB Mechanical Comprehension — Inclined Plane

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16. A small gear with 10 teeth drives a large gear with 30 teeth. For every 3 turns of the small gear, the large gear turns:
  1. A 30 times
  2. B 1 time
  3. C 9 times
  4. D 3 times

Explanation

The large gear turns 1 time. ASVAB Mechanical Comprehension tests gear ratios. The gear ratio = driven gear teeth ÷ drive gear teeth = 30 ÷ 10 = 3:1. This means the small (drive) gear must turn 3 times for the large (driven) gear to turn ONCE. So for 3 turns of the small gear, the large gear turns 3 ÷ 3 = 1 time. The larger gear turns SLOWER (fewer rotations) but with more torque. Calculating gear rotations from tooth counts is commonly tested.
Source: ASVAB Mechanical Comprehension — Gear Ratios

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17. To lift a heavy load with a lever using the least effort, where should you apply the force, and where should the fulcrum be?
  1. A The positions don't matter
  2. B Apply force close to the fulcrum
  3. C Apply force far from the fulcrum, with the fulcrum close to the load
  4. D Apply force at the fulcrum

Explanation

To minimize effort with a lever: apply the force FAR from the fulcrum (long effort arm) and place the fulcrum CLOSE to the load (short load arm). ASVAB Mechanical Comprehension tests lever mechanical advantage. MECHANICAL ADVANTAGE = effort arm length ÷ load arm length. A longer effort arm and shorter load arm give greater mechanical advantage (less force needed), but the effort must move a greater distance. This is why a long crowbar with the fulcrum near the load lifts heavy objects easily. The effort-arm/load-arm relationship is commonly tested.
Source: ASVAB Mechanical Comprehension — Lever Mechanical Advantage

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18. A screw is essentially which simple machine wrapped around a cylinder?
  1. A An inclined plane
  2. B A pulley
  3. C A wheel and axle
  4. D A lever

Explanation

A SCREW is essentially an INCLINED PLANE wrapped around a cylinder. ASVAB Mechanical Comprehension tests simple machines. The threads of a screw form a spiral inclined plane; turning the screw converts rotational motion into linear motion and provides mechanical advantage (a screw with closer threads requires more turns but less force). The six simple machines: lever, inclined plane, wheel and axle, pulley, wedge, and screw. A WEDGE is two inclined planes back-to-back. Recognizing the screw as a wrapped inclined plane is commonly tested.
Source: ASVAB Mechanical Comprehension — Screw

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19. If you want to increase the speed of a driven gear, the drive gear should be:
  1. A Larger than the driven gear
  2. B Smaller than the driven gear
  3. C Removed entirely
  4. D The same size as the driven gear

Explanation

To INCREASE the SPEED of the driven gear, the drive gear should be LARGER than the driven gear. ASVAB Mechanical Comprehension tests gear speed relationships. When a LARGER drive gear turns a SMALLER driven gear, the smaller gear spins FASTER (more rotations) but with LESS torque. Conversely, a small gear driving a large gear turns it slower but with more torque (force). Trade-off: speed vs torque. So for more speed on the driven gear, use a larger drive gear (or smaller driven gear). Gear speed/size relationships are commonly tested.
Source: ASVAB Mechanical Comprehension — Gear Speed

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20. How does a single fixed pulley help when lifting a load?
  1. A It removes the need for any force
  2. B It changes the direction of the force without reducing the amount of force needed
  3. C It reduces the force needed by half
  4. D It doubles the load

Explanation

A single fixed pulley (attached to a fixed point overhead) changes the direction of the force — letting you pull down to lift a load up — but it does not reduce the amount of force required; you still must pull with a force equal to the load's weight. To gain a mechanical advantage (reduce the force needed), you use a movable pulley or a combination of pulleys (a block and tackle), which trades reduced force for a longer length of rope pulled. Understanding that a fixed pulley redirects force while movable/multiple pulleys multiply it is a frequently tested simple-machine concept.
Source: ASVAB MC, Pulleys

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21. When two gears of different sizes mesh together, what happens to the smaller gear compared to the larger gear?
  1. A The smaller gear does not turn
  2. B The smaller gear turns faster but with less torque than the larger gear
  3. C The smaller gear turns slower
  4. D Both turn at exactly the same speed

Explanation

When a small gear meshes with a larger gear, the smaller gear turns faster but with less torque, while the larger gear turns slower but with more torque. This is because the teeth move at the same rate where they mesh, so the smaller gear must complete more revolutions to keep up. Gears trade speed for torque (turning force) just as levers and pulleys trade force for distance. Meshed gears also turn in opposite directions. Understanding the speed-versus-torque tradeoff in gear pairs — small gear faster/less torque, large gear slower/more torque — is essential mechanical comprehension content.
Source: ASVAB MC, Gears

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22. How does an inclined plane (ramp) make lifting a heavy object easier?
  1. A It makes the object lighter permanently
  2. B It reduces the object's weight
  3. C It removes gravity
  4. D It reduces the force needed by spreading the work over a longer distance

Explanation

An inclined plane (ramp) makes raising a heavy object easier by reducing the force needed to move it — but over a longer distance. Instead of lifting the full weight straight up, you push it up the gentler slope with less force, though you must move it farther. The total work (force × distance) is about the same (ignoring friction), but the reduced force is easier to apply. This is the mechanical advantage of a ramp: a longer, gentler ramp requires less force than a short, steep one. The inclined plane is one of the basic simple machines that trade force for distance.
Source: ASVAB MC, Inclined Plane

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23. What is mechanical advantage?
  1. A The weight of a machine
  2. B The factor by which a machine multiplies the input force
  3. C The energy a machine creates
  4. D The speed of a machine

Explanation

Mechanical advantage is the factor by which a simple machine multiplies the input (effort) force. For example, a mechanical advantage of 4 means the machine outputs four times the force you put in. It is calculated as the output force divided by the input force (or, ideally, the distance the effort moves divided by the distance the load moves). Machines like levers, pulleys, ramps, and gears provide mechanical advantage by trading reduced force for increased distance — they do not create energy. A higher mechanical advantage means less force is needed, but over a greater distance. This concept ties together all the simple machines.
Source: ASVAB MC, Mechanical Advantage

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