| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.23 |
| Score | 0% | 65% |
The pitch of the siren of an approaching ambulance changes as it approaches you. This is an example of which of the following?
refraction |
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sound radiation |
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Doppler effect |
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reflection |
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.
The energy posessed by a ball on the window ledge of a tall building is an example of what kind of energy?
gravitational |
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potential |
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kinetic |
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inherent |
Kinetic energy is the energy posessed by a moving object. Potential energy is stored energy in a stationary object based on its location, position, shape, or state.
Velocity is the rate at which an object changes position. What is the formula for velocity?
\(\vec{v} = \vec{d}t \) |
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\(\vec{v} = { t \over \vec{d} } \) |
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\(\vec{v} = { \vec{d} \over t } \) |
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none of these |
Velocity is the rate at which an object changes position. Rate is measured in time and position is measured in displacement so the formula for velocity becomes \(\vec{v} = { \vec{d} \over t } \)
Which of the following is not true of light waves?
travel faster than sound waves |
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are mechanical waves |
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can travel through a vacuum |
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are electromagnetic waves |
Unlike mechanical sound waves that require a physical medium for propagation, light waves are electromagnetic and can travel through empty space. Light waves are also much faster, travelling at 186,000 m/s vs. 343 m/s for sound waves.
Which of the following is not a medium for sound waves?
solid |
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vacuum |
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none of these is a medium for sound waves |
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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.