| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.32 |
| Score | 0% | 66% |
The pitch of the siren of an approaching ambulance changes as it approaches you. This is an example of which of the following?
sound radiation |
|
Doppler effect |
|
reflection |
|
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.
Changes to an object's speed or direction of motion are caused by which of the following?
kinetic energy |
|
work |
|
a force |
|
power |
Force is applied to change an object's speed or direction of motion.
Plant cells are surrounded by:
only a cell wall |
|
a cell membrane and a cell wall |
|
neither a cell membrane nor a cell wall |
|
only a cell membrane |
Animal cells are surrounded by a semipermeable membrane which allows for the transfer of water and oxygen to and from the cell. In plant cells, the cell membrane is surrounded by a somewhat rigid cell wall which provides the cell structure and support.
What part of the food chain serves only as food for other organisms?
decomposers |
|
secondary consumers |
|
producers |
|
primary consumers |
Producers (autotrophs) serve as a food source for other organisms. Typical producers are plants that can make their own food through photosynthesis and certain bacteria that are capable of converting inorganic substances into food through chemosynthesis
Convert -20C° to F°.
-4 |
|
-36 |
|
78 |
|
36 |
To convert from C° to F° use:
\(F° = {9 \over 5}C° + 32\)
\(F° = {9 \over 5}(-20) + 32\)
\(F° = {-180 \over 5} + 32\)
\(F° = -36 + 32 = -4\)