According to the information in the table, which of the following boys would hear a rock fall off of a cliff a kilometer away?
A. a boy sitting in a tree with his ear to the bark
B. a boy sitting on the grass
C. a boy swimming in the water
D. a boy lying down with his ear to the ground
D. a boy lying down with his ear to the ground
To determine which of the boys would hear a rock fall off of a cliff, we need to consider the method in which sound travels and the characteristics of different materials for conducting sound.
Sound is transmitted as a wave through different mediums such as air, solids, and liquids. In general, sound travels faster through solids or liquids than through air.
The best conductor of sound among the options provided is a solid, with direct contact to the source of the sound being the most effective. Therefore, the boy who is most likely to hear the rock fall off the cliff is the one who can best transmit sound waves to his ears.
Looking at the given options:
A. A boy sitting in a tree with his ear to the bark: Although the tree may conduct some sound, it is not a direct contact with the ground or the water, making it less likely for him to hear the sound.
B. A boy sitting on the grass: Grass is not a good conductor of sound, and he is not in direct contact with the ground or water. It is less likely for him to hear the sound as well.
C. A boy swimming in the water: Water is a better conductor of sound compared to air. Being submerged in water would allow the sound waves to propagate more effectively, making it more likely for this boy to hear the rock fall off the cliff.
D. A boy lying down with his ear to the ground: The ground is a solid surface, and it transmits sound waves effectively. Lying down on the ground with his ear close to it would allow the boy to hear the sound more clearly than the other options.
Therefore, the boy who is most likely to hear a rock fall off a cliff a kilometer away is option D: a boy lying down with his ear to the ground.
To determine which boy would hear a rock fall off of a cliff a kilometer away, we need to consider the different ways sound travels. Sound waves travel through a medium, such as air, and are transmitted through vibrations.
Based on this information, the boy who would most likely hear the rock fall off of a cliff a kilometer away is option D: a boy lying down with his ear to the ground. When lying on the ground, the boy's ear is in direct contact with the solid medium, allowing sound vibrations to be transmitted more effectively. This method of listening is known as bone conduction.
The other options -- a boy sitting in a tree with his ear to the bark, a boy sitting on the grass, and a boy swimming in the water -- are all less likely to hear the sound of a rock falling from a kilometer away because these mediums (tree bark, grass, and water) are not as efficient at transmitting sound vibrations as the solid ground.