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General Science

DNA is encoded through a combination of which of the following?

nucleotides

Deoxyribonucleic acid (DNA) is the molecule that contains genetic information. DNA is encoded through a combination of nucleotides that bind together in a specific double helix pattern.

Math Knowledge

On this circle, line segment CD is the:

radius

A circle is a figure in which each point around its perimeter is an equal distance from the center. The radius of a circle is the distance between the center and any point along its perimeter. A chord is a line segment that connects any two points along its perimeter. The diameter of a circle is the length of a chord that passes through the center of the circle and equals twice the circle's radius (2r).

Electronics Information

Use Ohm's Law to calculate the value of resistance in this circuit if voltage is 40 volts and current is 2 amps.

20 Ω

Ohm's law specifies the relationship between voltage (V), current (I), and resistance (R) in an electrical circuit: V = IR.

Solved for resistance, R = \( \frac{V}{I} \) = \( \frac{40}{2} \) = 20 Ω

General Science

Which of the following is not a characteristic of the Sun?

formed 2.6 billion years ago

The Sun is a G-type main-sequence star (G2V) but is informally known as a yellow dwarf star. Composed of 73% hydrogen and 25% helium, the hot plasma that makes up the Sun reaches 9,900°F (5,505°C) at the surface. It formed approximately 4.6 billion years ago and makes up 99.86% of the mass in the solar system.

Mechanical Comprehension

Connected gears of different numbers of teeth are used together to change which of the following charasteristics of the input force?

torque

Connected gears of different numbers of teeth are used together to change the rotational speed and torque of the input force. If the smaller gear drives the larger gear, the speed of rotation will be reduced and the torque will increase. If the larger gear drives the smaller gear, the speed of rotation will increase and the torque will be reduced.

General Science

__________ is caused by a lack of iron in the diet.

anemia

Anemia, which may cause weakness, dizziness, and headaches is caused by a lack of iron in the diet.

Mechanical Comprehension

If you have a gear train with two gears, the first with 32 teeth and the second with 4 teeth, how many revolutions does the second gear make for each revolution of the first gear?

The gear ratio (V_r) of a gear train is the product of the gear ratios between the pairs of meshed gears. Let N represent the number of teeth for each gear:

V_r = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) \( \frac{N_3}{N_4} \) ... \( \frac{N_n}{N_{n+1}} \)

In this problem, we have only two gears so the equation becomes:

V_r = \( \frac{N_1}{N_2} \) = \( \frac{32}{4} \) = 8

Mechanical Comprehension

A 290 lb. barrel is rolled up a 14 ft. ramp to a platform that's 2 ft. tall. What effort is required to move the barrel?

41.4 lbs.

This problem describes an inclined plane and, for an inclined plane, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance:

F_ed_e = F_rd_r

Plugging in the variables from this problem yields:

F_e x 14 ft. = 290 lbs. x 2 ft.
F_e = \( \frac{580 ft⋅lb}{14 ft.} \) = 41.4 lbs.

Word Knowledge

Heidi's grandfather was gruff, barking stern orders and hardly smiling.

surly

Rough or stern in manner or speech.

Electronics Information

General current flow in a transistor is from __________ to __________.

collector, emitter

The transistor is the foundation of modern electronic devices. It is made entirely from semiconductor material (making it a solid state device) and can serve many different functions in a circuit including acting as a switch, amplifier, or current regulator. A transistor works by allowing a small amount of current applied at the base to control general current flow from collector to emitter through the transistor.