<span> B. A person moving a ball through a stream of water</span>
Choices 'C' and 'D' are both correct.
(Except in 'C', changing the temperature from 1°C to 3°C is not usually
described as 'cooling', and it's not the water's 'mass' that changes. But
water does contract in volume during that change.)
Explanation:
Echoes occur due to the reflection of sound from any obstacle, but not all the reflected sound waves lead to the phenomenon of echo. For the echo to be heard it actually depends upon the human perception as well, human ears can encounter the difference between the sound wave directly form the source and the reflected sound waves only if there is a minimum time gap of one-tenth of a second. For this time gap in the atmosphere at normal temperature and pressure the obstacle must be at least 7 meters away from the sound source.
Answer:
Explanation:19,2 or 0/4 or 5 or 40,4
Answer:
Explanation:
As per Kepler's III law we know that time period of revolution of satellite or planet is given by the formula
now for the time period of moon around the earth we can say
here we know that
= mass of earth
Now if the same formula is used for revolution of Earth around the sun
here we know that
= mass of Sun
now we have
