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Mechanical Comprehension

If a 25 lbs. weight is placed 3 ft. from the fulcrum at the blue arrow and the green box is 6 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?

12.5 lbs.

To balance this lever the torques on each side of the fulcrum must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

R_ad_a = R_bd_b

where a represents the left side of the fulcrum and b the right, R is resistance (weight) and d is the distance from the fulcrum.

Solving for R_a, our missing value, and plugging in our variables yields:

R_a = \( \frac{R_bd_b}{d_a} \) = \( \frac{25 lbs. \times 3 ft.}{6 ft.} \) = \( \frac{75 ft⋅lb}{6 ft.} \) = 12.5 lbs.

General Science

Which of blood component carries oxygen?

red blood cells

Blood is created in bone marrow and is made up of cells suspended in liquid plasma. Red blood cells carry oxygen, white blood cells fight infection, and platelets are cell fragments that allow blood to clot.

Mechanical Comprehension

The work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. This defines which of the following?

work-energy theorem

The work-energy theorem states that the work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. Simply put, work imparts kinetic energy to the matter upon which the work is being done.

General Science

-40°F is how many °C?

-40

The formula to convert from F° to C° is:

\(C° = {5 \over 9} (F° - 32)\)

plugging in our values gives:

\(C° = {5 \over 9} (-40 - 32)\)

\(C° = {5 \over 9} (-72) = {{-72 \times 5} \over 9}\)

\(C° = {-360 \over 9}\)

\(C° = -40\)

Automotive Information

Exhaust gases from cylinder exhaust valves are collected by the:

exhaust manifolds

The cast iron exhaust manifolds collect engine exhaust gas from multiple cylinder exhaust valves and deliver it to the exhaust pipe. Exhaust manifolds can be generic or specially tuned (header pipes) to the engine. Header pipes deliver higher performance but are more expensive and less durable.

Electronics Information

The voltage output of a transformer primarily depends on which of the following?

the number of turns in the wire of the coils

A transformer utilizes an inductor to increase or decrease the voltage in a circuit. AC flowing in a coil wrapped around an iron core magnetizes the core causing it to produce a magnetic field. This magnetic field generates a voltage in a nearby coil of wire and, depending on the number of turns in the wire of the primary (source) and secondary coils and their proximity, voltage is induced in the secondary coil.

Word Knowledge

Authoritarian most nearly means:

strict

Favoring absolute obedience to authority.

Mechanical Comprehension

Which of the following is not a type of bridge?

block

The six basic bridge forms are beam, truss, arch, cantilever, cable, and suspension.

General Science

Momentum is a measure of how difficult it is for a moving object to stop. Which of the following is the formula for momentum?

\(\vec{p} = m\vec{v}\)

Momentum is a measure of how difficult it is for a moving object to stop and is calculated by multiplying the object's mass by its velocity: \(\vec{p} = m\vec{v}\). Like velocity, momentum is a vector quantity as it expresses force applied in a specific direction.

Automotive Information

Gases from combustion are pushed out through the exhaust valve as the piston travels up the cylinder to top dead center. This describes which engine stroke?

exhaust

During the exhaust stroke, just before the piston reaches bottom dead center the exhaust valve opens. The resulting gases from combustion are then pushed out through the exhaust valve as the piston travels up the cylinder to top dead center, completing stroke four of the four-stroke piston cycle.