| 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?
Doppler effect |
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reflection |
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sound radiation |
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refraction |
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.
An endoskeleton (internal skeleton) is a charateristic of __________ animals, including humans.
arthropod |
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sentient |
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vertebrate |
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spiny |
An endoskeleton (internal skeleton) is a charateristic of vertebrate animals, including humans.
Which of the following is not a characteristic of the Sun?
is a yellow dwarf star |
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formed 2.6 billion years ago |
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makes up over 99% of the mass of the solar system |
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is composed of hydrogen and helium |
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.
The rate of vibration of sound is called:
volume |
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frequency |
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amplitude |
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period |
The rate of vibration of sound is called frequency and is measured in hertz (Hz). One hertz is one repetition per second and sounds with high frequency have a higher pitch than sounds with lower frequency. Humans can hear sounds in the range of 20 Hz to 20 kHz.
DNA is encoded through a combination of which of the following?
nucleotides |
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helix |
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gametes |
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genes |
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.