| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.31 |
| Score | 0% | 66% |
A biological community of interacting organisms and their physical environment is known as:
community |
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population |
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ecosystem |
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biome |
An ecosystem is a biological community of interacting organisms and their physical environment. This includes both the biotic (living) and abiotic (non-living).
Acceleration is the rate of change of velocity per unit of time. Which of these is the formula for acceleration?
\(\vec{a} = { t \over \Delta \vec{v} }\) |
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\(\vec{a} = { \Delta \vec{v} \over t }\) |
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\(\vec{a} = { \vec{v} \over t }\) |
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\(\vec{a} = \Delta \vec{v} t \) |
Acceleration is the rate of change of velocity per unit of time. In physics, the delta symbol (\(\Delta\)) represents change so the formula for acceleration becomes \(\vec{a} = { \Delta \vec{v} \over t }\)
Changes to an object's speed or direction of motion are caused by which of the following?
kinetic energy |
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power |
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a force |
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work |
Force is applied to change an object's speed or direction of motion.
The pitch of the siren of an approaching ambulance changes as it approaches you. This is an example of which of the following?
Doppler effect |
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reflection |
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refraction |
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sound radiation |
The Doppler effect occurs when the source or listener (or both) of sound waves is moving. If they're moving closer together, the listener perceives the sound with a higher pitch and, when they're moving apart, the listener perceives the sound with a lower pitch.
Cirrus clouds generally occur in what kind of weather?
stormy |
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fair |
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hot |
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freezing |
Cirrus clouds are thin, wispy high-altitude clouds composed of ice crystals that originate from the freezing of supercooled water droplets. Cirrus clouds generally occur in fair weather and point in the direction of air movement at their elevation.