| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.11 |
| Score | 0% | 62% |
Which of the following is not a medium for sound waves?
vacuum |
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none of these is a medium for sound waves |
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solid |
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liquid |
A vibrating object produces a sound wave that travels outwardly from the object through a medium (any liquid or solid matter). The vibration disturbs the particles in the surrounding medium, those particles disturb the particules next to them, and so on, as the sound propagates away from the vibration.
Changes to an object's speed or direction of motion are caused by which of the following?
power |
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a force |
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work |
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kinetic energy |
Force is applied to change an object's speed or direction of motion.
Food is mixed with gastric acid and pepsin in the __________ to help break down protein.
stomach |
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small intestine |
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large intestine |
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mouth |
Food is mixed with gastric acid and pepsin in the stomach to help break down protein.
In the food chain, omnivores may be which of the following?
primary or tertiary consumers |
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secondary consumers or scavengers |
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secondary or tertiary consumers |
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primary or secondary consumers |
Secondary or tertiary consumers may be omnivores.
The fossil record is a product of which period of Earth's history?
Cenozoic |
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Cambrian |
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Cretaceous |
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Jurassic |
The Cambrian period is one of the most significant geological time periods. Lasting about 53 million years, it marked a dramatic burst of changes in life on Earth known as the Cambrian Explosion. It is from this period that the majority of the history of life on Earth, as documented by fossils, is found. Called the fossil record, the layering of these mineralized imprints of organisms preserved in sedementary rock have allowed geologists to build a historical record of plant and animal life on Earth.