ASVAB — All Questions

In which of these is the fulcrum located between the effort and the load?

• a.a wheelbarrow being lifted up
• b.a nutcracker being squeezed
• c.a claw hammer pulling a nail✓
• d.a pair of tweezers gripping

The hammer head rests on the board as a fulcrum, with the hand above it and the nail below, which makes it a first-class lever. A wheelbarrow and a nutcracker put the load between fulcrum and effort, and tweezers put the effort in the middle.

A crowbar is pivoted so that the effort arm is 6 feet and the load arm is 2 feet. How much effort is needed to lift a 300-pound load?

• a.100 pounds✓
• b.900 pounds
• c.150 pounds
• d.75 pounds

Balancing moments gives effort x 6 = 300 x 2, so the effort is 100 pounds. The bar multiplies force three times, and the hand must move three times as far.

What does a single fixed pulley accomplish?

• a.it changes the direction of the pull✓
• b.it cuts the required force in half
• c.it doubles the load that can be lifted
• d.it shortens the distance the rope moves

A fixed pulley has a mechanical advantage of one, so the effort equals the load. Its value is that a downward pull can raise a load upward.

A single movable pulley is used to raise a load. Compared with lifting the load directly, the effort needed is

• a.twice as large
• b.four times as large
• c.half as large✓
• d.exactly the same

Two rope sections support the movable pulley, so each carries half the load. The trade is that the rope must be pulled twice as far.

A 20-tooth gear turning at 90 revolutions per minute drives a meshed 60-tooth gear. How fast does the larger gear turn?

• a.90 revolutions per minute
• b.270 revolutions per minute
• c.30 revolutions per minute✓
• d.45 revolutions per minute

Speed is inversely proportional to tooth count, so a gear with three times the teeth turns one-third as fast: 90 x 20 / 60 = 30 rpm.

Two external gears of different sizes are meshed directly together. How do they turn?

• a.at the same speed
• b.in the same direction
• c.in opposite directions✓
• d.at exactly the same torque

Where the teeth meet, the surfaces move together, which forces the two gears to rotate opposite ways. Adding a third idler gear between them restores the same direction.

A ramp 12 feet long is used to raise a 200-pound crate to a platform 3 feet high. Ignoring friction, how much force is needed to push the crate up the ramp?

• a.50 pounds✓
• b.75 pounds
• c.25 pounds
• d.150 pounds

The ramp's mechanical advantage is length divided by height, or 12 / 3 = 4, so the force is 200 / 4 = 50 pounds. The work is unchanged: a quarter of the force over four times the distance.

In a hydraulic press, a 50-pound force is applied to a piston with an area of 2 square inches. What force appears at a second piston of 20 square inches?

• a.50 pounds
• b.500 pounds✓
• c.200 pounds
• d.1,000 pounds

The pressure is 50 / 2 = 25 pounds per square inch throughout the fluid, and 25 x 20 = 500 pounds at the larger piston. The large piston moves only one-tenth as far.

A block presses down with 120 pounds over a contact area of 4 square inches. What pressure does it exert?

• a.480 pounds per square inch
• b.4 pounds per square inch
• c.116 pounds per square inch
• d.30 pounds per square inch✓

Pressure is force divided by area: 120 / 4 = 30 pounds per square inch.

Two tanks are filled with water to the same depth, but one is much wider than the other. How does the water pressure at the bottom compare?

• a.it is greater in the wide tank
• b.it is greater in the narrow tank
• c.it is the same in both✓
• d.it depends on the tank material

Pressure in a liquid at rest depends on depth and density, not on the shape or the total volume of the container.

A 180-pound crate hangs from a 10-foot pole carried by two workers at its ends. If the crate hangs 3 feet from the first worker, how much of the load does that worker carry?

• a.126 pounds✓
• b.90 pounds
• c.54 pounds
• d.150 pounds

Taking moments about the far worker, the near worker's share is 180 x 7 / 10 = 126 pounds. The worker closer to the load always carries more of it.

A mechanic switches from a 10-inch wrench to a 20-inch wrench and pulls with the same force. The torque applied to the bolt is

• a.four times as great
• b.half as great
• c.the same
• d.twice as great✓

Torque is force multiplied by the distance from the pivot, so doubling the handle length doubles the torque for an unchanged pull.

A screw thread is best described as which simple machine?

• a.a first-class lever
• b.a wheel and axle
• c.an inclined plane✓
• d.a pulley

A thread is an inclined plane wrapped around a cylinder, which is why turning the screw many times advances it a short distance with great force.

Two screws are the same diameter, but one has finer threads than the other. Compared with the coarse screw, the fine screw offers

• a.less holding force per turn
• b.much less mechanical advantage
• c.greater mechanical advantage✓
• d.greater advance per turn

A finer thread advances a shorter distance per turn, so the same turning effort produces more force. The trade is that more turns are required.

Which change would make a loaded hand truck harder to tip over?

• a.using smaller wheels
• b.lowering the center of gravity✓
• c.narrowing the wheel base
• d.raising the center of gravity

Stability improves as the center of gravity drops and as the base of support widens, because the load must be tilted farther before its weight falls outside the base.

What is the purpose of a flywheel on an engine?

• a.to reverse the direction of rotation
• b.to smooth out changes in speed✓
• c.to cool the moving parts
• d.to increase the fuel supply

A heavy flywheel stores rotational energy during the power stroke and gives it back during the others, evening out the shaft speed.

Two pulleys of different sizes are joined by an ordinary uncrossed belt. How do they turn?

• a.with equal torque
• b.in opposite directions
• c.in the same direction✓
• d.at the same speed

An open belt carries motion around both wheels the same way. Crossing the belt reverses the driven pulley.

The property that allows a metal to be drawn out into wire is called

• a.brittleness
• b.hardness
• c.ductility✓
• d.conductivity

Ductility is the ability to deform under tension without breaking. Hardness resists scratching and denting, and a brittle metal would snap instead of stretching.

The property that allows a metal to be hammered into thin sheets is called

• a.elasticity
• b.malleability✓
• c.hardness
• d.brittleness

Malleability is the ability to deform under compression without cracking. Elasticity instead describes a material that springs back to its original shape.

A beam is supported at both ends and loaded at its midpoint. Where does the greatest bending occur?

• a.at the left support
• b.just inside each support
• c.at the right support
• d.at the midpoint✓

Bending moment in a simply supported beam builds from zero at each support to a maximum under the load at midspan.

Which shape gives a framework its rigidity without relying on stiff joints?

• a.the square
• b.the hexagon
• c.the triangle✓
• d.the rectangle

A triangle cannot change shape unless a side changes length, so trusses are built from triangles. A square frame can rack into a parallelogram.

Why is it easier to move a heavy crate on rollers than to slide it across the floor?

• a.the floor becomes smoother
• b.gravity is reduced
• c.rolling friction is lower✓
• d.the crate weighs less

Rolling contact deforms very little and produces far less resistance than sliding contact. The crate's weight is unchanged.

A block and tackle is rigged with four rope sections supporting the movable block. Ignoring friction, how much effort raises a 480-pound load?

• a.120 pounds✓
• b.480 pounds
• c.60 pounds
• d.240 pounds

Four supporting sections share the load, so the effort is 480 / 4 = 120 pounds. The rope must be pulled four feet for every foot the load rises.

A small gear drives a much larger gear. At the larger gear, compared with the smaller one, the output has

• a.less torque and more speed
• b.less torque and less speed
• c.more torque and more speed
• d.more torque and less speed✓

Gearing trades speed for turning force. Power stays roughly constant, so the slower shaft carries the greater torque.

A cam and follower are used to produce which kind of motion?

• a.back-and-forth motion from rotation✓
• b.a steady increase in speed
• c.rotation from back-and-forth motion
• d.rotation at a constant torque

A rotating cam lobe pushes the follower out and lets it return, converting rotary motion into reciprocating motion. Engine valves are opened this way.

One spring stretches 4 inches under a load. If two identical springs share the same load side by side, how far does each stretch?

• a.4 inches
• b.2 inches✓
• c.8 inches
• d.1 inch

Each spring now carries half the load, so each stretches half as far, or 2 inches. Springs sharing a load this way behave as one stiffer spring.

What is the main job of the alternator?

• a.to regulate the flow of fuel to the engine
• b.to store current for the starter motor
• c.to start the engine when the driver turns the key
• d.to recharge the battery while the engine runs✓

The alternator is driven by the engine and supplies the electrical system while replacing the charge the starter drew from the battery. Cranking the engine is the starter motor's job.

What does the thermostat in a cooling system do?

• a.it warns the driver of an overheated engine
• b.it pumps coolant through the engine block
• c.it blocks coolant flow until the engine warms up✓
• d.it cools the coolant before it reaches the engine

A closed thermostat keeps coolant out of the radiator so the engine reaches operating temperature quickly, then opens to let heat escape. The water pump does the pumping.

Besides lubricating, which of the following does engine oil also do?

• a.it carries heat away from moving parts✓
• b.it raises the compression in the cylinders
• c.it improves the spark at the plug gap
• d.it cools the passenger compartment

Oil films the bearings and rings, but it also carries heat out of the engine and suspends contaminants until the filter traps them.

What is the correct order of the strokes in a four-stroke gasoline engine?

• a.intake, compression, power, exhaust✓
• b.intake, power, compression, exhaust
• c.power, intake, compression, exhaust
• d.compression, intake, power, exhaust

The piston draws in the mixture, compresses it, is driven down by the burning charge, and then pushes the spent gases out.

How is the fuel mixture ignited in a diesel engine?

• a.by exhaust gas recirculation
• b.by a heated glow plug
• c.by a spark plug
• d.by the heat of compression✓

A diesel compresses air until it is hot enough to ignite the fuel injected into it, so no spark or arc is needed. Glow plugs, where fitted, only warm the chamber for cold starting.

What does the clutch do in a manual transmission vehicle?

• a.it holds the vehicle still on a hill
• b.it chooses which gear ratio will be used
• c.it locks the drive wheels together
• d.it disconnects engine and transmission✓

Pressing the clutch pedal separates the flywheel from the transmission input shaft so gears can be changed without the engine driving them. Choosing the ratio is the gearbox's job, not the clutch's.

In a disc brake, the pads are squeezed against which part?

• a.the rotor✓
• b.the axle
• c.the drum
• d.the wheel rim

A caliper presses the pads onto both faces of the rotor that spins with the wheel. Drums belong to the other main brake design.

What is the purpose of the catalytic converter?

• a.it makes exhaust gases less harmful✓
• b.it quiets the noise of the exhaust
• c.it increases engine power output
• d.it cools the exhaust manifold

The converter promotes reactions that turn carbon monoxide and unburned fuel into carbon dioxide and water. The muffler is what quiets the exhaust.

What does the differential allow the drive wheels to do?

• a.turn at different speeds in a corner✓
• b.turn at exactly the same speed
• c.spin freely when the car is parked
• d.reverse without shifting gears

In a turn the outside wheel travels farther than the inside wheel, and the differential lets them rotate at different rates while both receive power.

A tire that is consistently underinflated will usually show wear

• a.evenly across the entire tread width
• b.on one edge of the tread only
• c.on both outer edges of the tread✓
• d.down the center of the tread

Low pressure lets the tread bow upward in the middle so the shoulders carry the load. Overinflation produces the opposite pattern, wear down the center.

What does antifreeze added to the cooling system do?

• a.it thickens the coolant to improve the heat transfer
• b.it protects against freezing but not boiling over
• c.it protects against both freezing and boiling over✓
• d.it protects against boiling over but not freezing

A glycol and water mixture protects against freezing in winter and against boil-over in summer, which is why it stays in the system year round.

What component builds the hydraulic pressure when the brake pedal is pressed?

• a.the master cylinder✓
• b.the proportioning valve
• c.the brake booster
• d.the wheel bearing

The pedal pushes a piston in the master cylinder, which sends pressurized fluid to each wheel. The booster only reduces the pedal effort required.

A saw designed to cut across the grain of a board is called

• a.a crosscut saw✓
• b.a coping saw
• c.a rip saw
• d.a metal hacksaw

Crosscut teeth are filed to sever wood fibers across the grain, while rip teeth act like tiny chisels for cutting along the grain. A hacksaw is for metal.

Which tool measures to the nearest thousandth of an inch?

• a.a framing square
• b.a folding rule
• c.a tape measure
• d.a micrometer✓

A micrometer's precision screw and vernier scale resolve 0.001 inch. A rule or tape measure is generally read to a sixteenth of an inch.

What is a hand plane used for?

• a.driving fasteners in flush
• b.boring holes through a board
• c.cutting joints in sheet metal
• d.smoothing a wood surface✓

A plane's blade projects slightly below the sole and removes a thin shaving with each pass, flattening and smoothing the surface.

A hand file cuts on which stroke?

• a.neither, it only polishes
• b.both strokes equally
• c.the return stroke
• d.the forward stroke✓

File teeth point forward, so cutting happens on the push. Dragging the file back under pressure dulls the teeth.

A wood chisel should be struck with

• a.a claw hammer
• b.a ball-peen hammer
• c.a mallet✓
• d.a heavy wrench

A wooden or soft-faced mallet drives the chisel without mushrooming its handle. Steel hammer faces damage the chisel and can chip.

Which tool cuts internal threads inside a drilled hole?

• a.a countersink
• b.a tap✓
• c.a reamer
• d.a die

A tap cuts threads inside a hole and a die cuts threads on the outside of a rod. A reamer only sizes and smooths an existing hole.

Why is a countersink used before driving a flat-head screw?

• a.so the head finishes flush✓
• b.so the screw grips harder
• c.so the hole is sealed against water
• d.so the screw comes out faster

The countersink cuts a cone-shaped recess that matches the underside of a flat head, letting it finish level with the surface.

Why is a pilot hole drilled before driving a wood screw into hardwood?

• a.to keep the screw from rusting
• b.to make the screw hold more tightly
• c.to allow the screw to be countersunk
• d.to keep the wood from splitting✓

The screw's shank displaces wood as it enters, and in dense hardwood that pressure can split the board. A pilot hole removes that material in advance.

On sandpaper, a higher grit number indicates

• a.a wider sheet
• b.a finer abrasive✓
• c.a coarser abrasive
• d.a tougher backing

Grit numbers count the particles that pass a screen, so a larger number means smaller particles and a finer finish.

A ball-peen hammer is intended mainly for

• a.metalwork✓
• b.setting tile
• c.driving nails
• d.shaping stone

The rounded peen is used for riveting and shaping metal. Nails are driven with a claw hammer, which also pulls them.

What is a miter box used for?

• a.storing chisels in order
• b.measuring the board thickness
• c.clamping the stock to a bench
• d.guiding a saw at an angle✓

The slots in a miter box hold the saw at a fixed angle, commonly 45 or 90 degrees, so repeated cuts match.

A plumb bob is used to check

• a.that a corner is square
• b.that a line is vertical✓
• c.that a board is flat
• d.that a line is horizontal

A weight hanging on a string settles along the direction of gravity, which is by definition vertical. A spirit level checks horizontal, and a square checks corners.