ASVAB Mechanical Comprehension Test — Questions and Answers

Question 1: How much force is needed to lift the 10Kg weight?

2 Kg
5 Kg (Correct answer)
10 Kg
20 Kg

Correct answer: 5 Kg

This question likely refers to a simple machine, such as a pulley system, designed to provide mechanical advantage. If the system has a mechanical advantage of 2, it means the force required to lift the weight is halved. Therefore, to lift a 10 Kg weight, only 5 Kg of force would be needed.

Question 2: The smaller gear has 8 teeth, and the larger gear has 16 teeth. When the larger gear makes 12 revolutions, how many revolutions will the smaller gear make?

8
16
18
24 (Correct answer)

Correct answer: 24

The relationship between two meshed gears is inversely proportional to their number of teeth. Since the larger gear has 16 teeth and the smaller gear has 8 teeth, the smaller gear will rotate twice for every single rotation of the larger gear. Therefore, if the larger gear makes 12 revolutions, the smaller gear will make 12 * 2 = 24 revolutions.

Question 3: Which of the following is the basis for Pascal’s Law?

The amplification of force in a hydraulic system. (Correct answer)
The relationship between force and volume of a liquid.
The definition of pressure as pounds per square inch.
The manner in which liquids conform to their container.

Correct answer: The amplification of force in a hydraulic system.

Pascal's Law states that a pressure change at any point in a confined incompressible fluid is transmitted throughout the fluid such that the same change occurs everywhere. This principle is the fundamental basis for how hydraulic systems work, allowing a small force applied over a small area to generate a much larger force over a larger area, thus amplifying force.

Question 4: An 80-lb child is sitting on one end of a seesaw. If another 80-lb child jumps from a high platform onto the other end of the seesaw, what will happen?

The first child will stay stationary on the ground.
The second child will bounce off the seesaw into the air.
The first child will bounce off the seesaw into the air.
The first child will be lifted into the air, but remain seated. (Correct answer)

Correct answer: The first child will be lifted into the air, but remain seated.

When the second 80-lb child jumps onto the seesaw, their momentum is transferred to the seesaw and the first child. While the impact will cause the seesaw to move rapidly, the first child, being seated and having the same weight, will be lifted into the air due to this transfer of energy and momentum, rather than bouncing off completely.

Question 5: What is a vector quantity?

Gravity (Correct answer)
Magnitude
Volume
Mass

Correct answer: Gravity

A vector quantity is a physical quantity that possesses both magnitude (size) and direction. Gravity is a force, and forces are inherently vector quantities because they act in a specific direction (towards the center of mass) and have a measurable strength. In contrast, options like magnitude, volume, and mass are scalar quantities, which only have magnitude and no associated direction.

Question 6: Which of the following describes the relationship between kinetic energy, mass, and velocity?

KE = ½ m2 v
(1/3)(KE) = m/v2
2(KE) = mv2 (Correct answer)
3(KE) = m2v

Correct answer: 2(KE) = mv2

The fundamental formula for kinetic energy (KE) is KE = ½ mv², where 'm' represents mass and 'v' represents velocity. To express the relationship in the form of the correct answer, we can multiply both sides of this equation by 2. This manipulation yields 2(KE) = mv², which accurately describes the relationship between kinetic energy, mass, and velocity.

Question 7: One horsepower is equivalent to

724 watts
746 watts (Correct answer)
768 watts
782 watts

Correct answer: 746 watts

Horsepower (hp) is a traditional unit of power, commonly used to rate engines and motors, while watts (W) are the standard unit of power in the International System of Units (SI). The conversion factor between these two units is a widely accepted standard. Specifically, one horsepower is precisely equivalent to 746 watts.

Question 8: What type of simple machine is pictured above?

Fulcrum
First-class lever
Second-class lever (Correct answer)
Third-class lever

Correct answer: Second-class lever

A second-class lever is characterized by the arrangement where the load is positioned between the fulcrum (the pivot point) and the effort (where the force is applied). This configuration always provides a mechanical advantage, meaning a smaller effort force can lift a larger load. Common examples of second-class levers include a wheelbarrow or a nutcracker.

Question 9: At minimum, how many pulleys are there in a block and tackle system?

One
Two (Correct answer)
Three
Four

Correct answer: Two

A block and tackle system is a combination of pulleys and ropes used to lift heavy loads with less force. To achieve this mechanical advantage, the system requires at least two pulleys. Typically, one pulley is fixed to a support, and at least one other pulley is movable, attached to the load.

Question 10: When torque increases, speed

remains the same
increases, then decreases
increases
decreases (Correct answer)

Correct answer: decreases

Torque is a rotational force, while speed refers to the rate of rotation or linear motion. In many mechanical systems, especially those involving power transmission, there is an inverse relationship between torque and speed for a given power output. If the power remains constant, increasing the torque applied will result in a decrease in the rotational speed, and vice versa.

Question 11: If a wedge is made longer relative to its height, how does the force increase?

The amount of lift is decreased as the wedge is moved horizontally. (Correct answer)
The amount of lift is increased as the wedge is moved horizontally.
The amount of lift is decreased as the wedge is moved vertically.
The amount of lift is increased as the wedge is moved vertically.

Correct answer: The amount of lift is decreased as the wedge is moved horizontally.

A wedge is a simple machine that converts a force applied to its blunt end into forces perpendicular to its inclined surfaces, used for splitting or lifting. If a wedge is made longer relative to its height, its angle becomes shallower, which increases its mechanical advantage. This means less input force is required to achieve a certain output force, but the trade-off is that for a given horizontal movement of the wedge, the amount of vertical lift or separation achieved will be decreased.

Question 12: If a man uses 200 N of force over a distance of 50 meters, how many joules of work are performed?

1,000
5,000
10,000 (Correct answer)
20,000

Correct answer: 10,000

Work is a measure of energy transferred when a force causes displacement. It is calculated by multiplying the force applied by the distance over which the force acts (Work = Force × Distance). In this scenario, a force of 200 Newtons (N) applied over a distance of 50 meters (m) results in 200 N × 50 m = 10,000 Joules (J) of work performed.

Question 13: What is a component of potential energy?

Upward reactive force
The energy of movement
Gravity’s relationship to mass (Correct answer)
Newtons and distance

Correct answer: Gravity’s relationship to mass

Potential energy is stored energy an object possesses due to its position or state. Gravitational potential energy, a common form, specifically depends on an object's mass, its height relative to a reference point, and the acceleration due to gravity. Therefore, gravity's relationship to mass is a critical component in determining an object's gravitational potential energy (PE = mgh).

Question 14: A fish tank at an aquarium contains several cubic feet of water (1 cubic foot of water = 62.5 pounds). If the fish tank is 6 feet deep, 12 feet wide, and 13 feet long, what’s the approximate pressure at the bottom of the tank in pounds per square inch?

2.0
2.5 (Correct answer)
3.0
3.5

Correct answer: 2.5

Pressure in a fluid is calculated as the force exerted per unit area. For a fluid column, this is equivalent to the weight of the fluid above a given area. First, calculate the weight of a 1-square-foot column of water 6 feet deep: 6 ft * 62.5 lbs/ft³ = 375 lbs/ft². To convert this to pounds per square inch (psi), divide by the number of square inches in a square foot (144 in²): 375 lbs / 144 in² ≈ 2.60 psi, which rounds to 2.5 psi.

Question 15: If Gear A turns counterclockwise, what other gears turn counterclockwise?

C and D (Correct answer)
B and D
C and B
B, C, and D

Correct answer: C and D

In a gear train, adjacent gears always rotate in opposite directions. If Gear A turns counterclockwise, the gear it meshes with (let's call it B) will turn clockwise. If Gear C then meshes with Gear B, Gear C will turn counterclockwise. If Gear D also meshes with Gear B, or if Gear D meshes with Gear C, the direction depends on the specific arrangement. However, for both C and D to turn counterclockwise, they must either be driven by a common clockwise gear or be part of a compound system where an even number of gears separate them from the initial counterclockwise motion of A.

Question 16: The well pictured above uses what type of simple machine to raise and lower a bucket?

Block and tackle
Third-class lever
Wedge
Wheel and axle (Correct answer)

Correct answer: Wheel and axle

A traditional well that uses a crank handle to raise and lower a bucket operates as a wheel and axle simple machine. The crank handle acts as the 'wheel' with a larger radius, and the cylindrical drum around which the rope winds acts as the 'axle' with a smaller radius. This configuration provides a mechanical advantage, allowing a smaller force applied to the crank to lift a heavier bucket.

Question 17: Weight is the

Amount of "stuff" in an object
Density of matter in an object
Gravity generated by an object
Force exerted on a object due to gravity (Correct answer)

Correct answer: Force exerted on a object due to gravity

Weight is defined as the force exerted on an object due to gravity. It is a measure of how strongly gravity pulls on an object's mass. Unlike mass, which is a fundamental property of matter and remains constant, weight can vary depending on the strength of the gravitational field an object is in.

Question 18: What is the advantage of a single pulley?

It allows you to lift something with less force
It changes the direction of the effort (Correct answer)
It diminishes the effects of gravity
It decreases the chances of injury

Correct answer: It changes the direction of the effort

A single fixed pulley does not provide any mechanical advantage in terms of reducing the amount of force required to lift an object. Its primary benefit lies in changing the direction of the effort force. This allows a person to pull downwards, often using their body weight, to lift an object upwards, which can be more convenient and ergonomic than lifting directly against gravity.

ASVAB Mechanical Comprehension Test

How much force is needed to lift the 10Kg weight?