| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.39 |
| Score | 0% | 68% |
Which of the following is not a characteristic of a ceramic?
low density |
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chemically stable |
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low corrosive action |
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high melting point |
Ceramics are mixtures of metallic and nonmetallic elements that withstand exteme thermal, chemical, and pressure environments. They have a high melting point, low corrosive action, and are chemically stable. Examples include rock, sand, clay, glass, brick, and porcelain.
On Earth, acceleration due to gravity (g) is approximately __________.
9.8 m/s2 |
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1 m/s2 |
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6.67 x 10-11 m/s2 |
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1 m/s |
Newton's Law of Univeral Gravitation defines the general formula for the attraction of gravity between two objects: \(\vec{F_{g}} = { Gm_{1}m_{2} \over r^2}\) . In the specific case of an object falling toward Earth, the acceleration due to gravity (g) is approximately 9.8 m/s2.
A wedge is most similar to what other type of simple machine?
first-class lever |
|
second-class lever |
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third-class lever |
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inclined plane |
The wedge is a moving inclined plane that is used to lift, hold, or break apart an object. A wedge converts force applied to its blunt end into force perpendicular to its inclined surface. In contrast to a stationary plane where force is applied to the object being moved, with a wedge the object is stationary and the force is being applied to the plane. Examples of a wedge include knives and chisels.
A box is resting on a smooth floor. Static friction is present:
at all times |
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when an attempt is made to move the box |
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if the coefficient of friction is greater than one |
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only if normal force is present |
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).
| 58.33 lbs. | |
| 175 lbs. | |
| 8 lbs. | |
| 233.33 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:
Rada = Rbdb
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 Rb, our missing value, and plugging in our variables yields:
Rb = \( \frac{R_ad_a}{d_b} \) = \( \frac{50 lbs. \times 7 ft.}{6 ft.} \) = \( \frac{350 ft⋅lb}{6 ft.} \) = 58.33 lbs.