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Mechanical Comprehension

A box is resting on a smooth floor. Static friction is present:

when an attempt is made to move the box

For any given surface, the coefficient of static friction is higher than the coefficient of kinetic friction. More force is required to initally get an object moving than is required to keep it moving. Additionally, static friction only arises in response to an attempt to move an object (overcome the normal force between it and the surface).

General Science

An element in the physical state of __________ maintains a constant volume but their shape depends upon the shape of their container.

liquid

In the liquid state, molecules flow freely around each other and exist at a higher temperature range than the same substance in a solid state. Liquids maintain a constant volume but their shape depends upon the shape of their container.

Word Knowledge

Epitaph most nearly means:

inscription

Brief statement honoring a dead person.

Mechanical Comprehension

Which of the following represents how much two materials resist sliding across each other?

coefficient of friction

Coefficient of friction (μ) represents how much two materials resist sliding across each other. Smooth surfaces like ice have low coefficients of friction while rough surfaces like concrete have high μ.

Mechanical Comprehension

Gear ratio indicates which of the following about two connected gears?

mechanical advantage

The mechanical advantage (amount of change in speed or torque) of connected gears is proportional to the number of teeth each gear has. Called gear ratio, it's the ratio of the number of teeth on the larger gear to the number of teeth on the smaller gear. For example, a gear with 12 teeth connected to a gear with 9 teeth would have a gear ratio of 4:3.

Mechanical Comprehension

The principle of conservation of mechanical energy states that, as long as no other forces are applied, what will remain constant as an object falls?

total mechanical energy

As an object falls, its potential energy is converted into kinetic energy. The principle of conservation of mechanical energy states that, as long as no other forces are applied, total mechanical energy (PE + KE) of the object will remain constant at all points in its descent.

Mechanical Comprehension

The green box weighs 10 lbs. and a 35 lbs. weight is placed 3 ft. from the fulcrum at the blue arrow. How far from the fulcrum would the green box need to be placed to balance the lever?

10.5 ft.

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 d_a, our missing value, and plugging in our variables yields:

d_a = \( \frac{R_bd_b}{R_a} \) = \( \frac{35 lbs. \times 3 ft.}{10 lbs.} \) = \( \frac{105 ft⋅lb}{10 lbs.} \) = 10.5 ft.

Word Knowledge

Onset most nearly means:

start

Beginning.

General Science

In the food chain, omnivores may be which of the following?

secondary or tertiary consumers

Secondary or tertiary consumers may be omnivores.

Arithmetic Reasoning

Convert 0.0006095 to scientific notation.

6.095 x 10^-4

A number in scientific notation has the format 0.000 x 10^exponent. To convert to scientific notation, move the decimal point to the right or the left until the number is a decimal between 1 and 10. The exponent of the 10 is the number of places you moved the decimal point and is positive if you moved the decimal point to the left and negative if you moved it to the right:

0.0006095 in scientific notation is 6.095 x 10^-4