| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.40 |
| Score | 0% | 68% |
The pitch of the siren of an approaching ambulance changes as it approaches you. This is an example of which of the following?
reflection |
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sound radiation |
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refraction |
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Doppler effect |
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.
In the food chain, bacteria and fungi convert the organic matter in the dead bodies of plants and animals into simple nutrients. Bacteria and fungi are:
primary consumers |
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scavengers |
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decomposers |
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producers |
Decomposers (saprotrophs) are organisms such as bacteria and fungi that break down the organic matter in the dead bodies of plants and animals into simple nutrients.
Absolute zero is which of the following?
the freezing point of oxygen |
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0°C |
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the coldest temperature possible in the universe |
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the freezing point of hydrogen |
In contrast to the Celsius scale (measured in degrees centigrade) that fixes 0° at the freezing point of water and the Fahrenheit scale that uses 32°, the Kelvin scale fixes 0 at absolute zero (-273°C) which is the lowest temperature possible in the universe.
Small rocks shed by asteroids and comets that reach the earth are called:
meteorites |
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meteoroids |
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meteors |
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shooting stars |
Smaller rocks shed by asteroids and comets are called meteoroids. When these rocks reach Earth's atmosphere, they burn up in the mesosphere and become meteors. If a meteor manages to reach the Earth, it is called a meteorite.
"The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object." This describes which of Newton's laws of motion?
fourth |
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second |
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third |
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first |
Newton's second law of motion states that The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object. This law basically means that the greater the mass of an object, the more force is needed to overcome its inertia.