Mechanical Comprehension — ASVAB practice questions

In a wheelbarrow the wheel is at the front, the load sits in the tray in the middle, and the operator lifts the handles at the rear. This arrangement is an example of which lever class?

1. First class, with the fulcrum between effort and load
2. Second class, with the load between fulcrum and effort
3. Third class, with the effort between fulcrum and load
4. Not a lever at all, because the fulcrum is a rolling wheel

Answer: B — Second class, with the load between fulcrum and effort

B) Correct — the wheel axle is the fulcrum, the load is in the middle and the effort is at the handles, which defines a second-class lever. A) tempts because a seesaw layout is the most memorized case. C) tempts because a shovel or forearm fits that order, not a wheelbarrow. D) tempts because the fulcrum rolls, but a rolling pivot is still a fulcrum.

A wheel-and-axle works because:

1. Force on the larger wheel produces larger force at the smaller axle (trade-off in distance)
2. The smaller axle multiplies speed without changing force
3. Wheels store energy
4. Axles reduce friction only

Answer: A — Force on the larger wheel produces larger force at the smaller axle (trade-off in distance)

A) Effort on the rim moves through a longer distance; axle moves shorter with more force. B) That's the opposite direction. C) Not energy storage. D) Friction is secondary.

Two loaded hand trucks are identical except that one carries its cargo low and the other stacks the same cargo high. The low-loaded truck is harder to tip because of which factor?

1. It weighs more overall than the tall stacked load does
2. Its wheels experience much less rolling friction on the floor
3. Its center of gravity is lower and stays over the wheelbase
4. Gravity acts more strongly on objects that are nearer the ground

Answer: C — Its center of gravity is lower and stays over the wheelbase

C) Correct — a lower center of gravity must be tilted farther before it passes outside the base of support, so stability improves. A) tempts because heavier feels steadier, but the loads are equal. B) tempts because friction affects rolling effort, not tipping. D) tempts as a misconception; gravity does not measurably strengthen over a few feet.

Gear A has 10 teeth and drives Gear B with 30 teeth. The gear ratio is:

1. 1:3
2. 3:1
3. 1:30
4. 10:30 = 10:3

Answer: A — 1:3

Driver:driven = 10:30 = 1:3 (B turns at 1/3 the speed). A) Correct. B) Reversed. C/D) Misreductions.

A 12-tooth drive gear meshes directly with a 36-tooth driven gear. Compared with the drive gear, the driven gear turns how?

1. Three times as fast and in the same direction
2. One third as fast and in the same direction
3. One third as fast and in the opposite direction
4. Three times as fast and in the opposite direction

Answer: C — One third as fast and in the opposite direction

C) Correct — a 12-to-36 mesh is a 3-to-1 reduction, so the driven gear turns one third as fast, and directly meshed external gears always counter-rotate. A) tempts by inverting the ratio and forgetting reversal. B) tempts with the right speed but keeps direction, which only an idler or belt loop would do. D) tempts by inverting the ratio while getting direction right.

In a hydraulic system, pressure applied at one piston is:

1. Reduced at the other piston
2. Lost as heat entirely
3. Converted to electricity
4. Transmitted equally throughout the fluid (Pascal's principle)

Answer: D — Transmitted equally throughout the fluid (Pascal's principle)

A) Pressure transmits equally; force changes with area. D) Pascal's principle. C) Not electric. B) Some friction loss but not entire energy.

If Gear B is larger than Gear A, then compared with Gear A, Gear B turns:

1. Faster with more torque
2. Slower with more torque
3. Faster with less torque
4. Slower with less torque

Answer: B — Slower with more torque

A) Mismatch. B) Larger driven gear: slower, more torque. C/D) Wrong combos.

A sealed hydraulic system has a small input piston and a much larger output piston. Pressing the small piston lifts a heavy load on the large one. The principle at work states which of the following?

1. Pressure applied to a confined fluid is transmitted undiminished
2. A submerged body is buoyed up by the weight of fluid displaced
3. Fluid speeds up and its pressure falls as a passage narrows sharply
4. Force multiplies because liquids compress under heavy loading

Answer: A — Pressure applied to a confined fluid is transmitted undiminished

A) Correct — Pascal's principle says the pressure is the same throughout, so the larger area produces a larger force. B) tempts because it is Archimedes' principle, correct physics for the wrong question. C) tempts because it is Bernoulli's principle, which governs flow, not static lift. D) tempts by a common misconception; hydraulics work precisely because liquids barely compress.

A wedge is best described as:

1. Two inclined planes back-to-back
2. A rotating disk
3. A bent lever
4. A cylinder with threads

Answer: A — Two inclined planes back-to-back

A) An axe or chisel = back-to-back inclined planes. B) Wheel. C) Lever. D) Screw.

Friction in a machine typically:

1. Increases efficiency
2. Reduces efficiency by converting some energy to heat
3. Has no effect
4. Stores energy

Answer: B — Reduces efficiency by converting some energy to heat

A) Opposite. B) Friction wastes energy as heat. C/D) Wrong.

Name the six classic simple machines.

Lever, wheel and axle, pulley, inclined plane, wedge, and screw.

What is Pascal's principle and how does a hydraulic jack use it?

Pressure applied to a confined fluid transmits equally in all directions, and pressure equals force divided by area. • A small piston pushing on a much larger piston multiplies force in proportion to the area ratio.

Lever advantage formula?

Mechanical advantage = effort arm / load arm. Longer effort arm = less force needed.

When two meshed gears turn, how do direction and speed relate?

Meshed gears turn in opposite directions. • The smaller gear turns faster: a 10-tooth gear driving a 30-tooth gear makes the driven gear turn one third as fast with three times the torque.