Please help me out 1.Anna could easily hear her echo when she shouted in her school's multipurpose hall. Later she shouted in the same manner in her room at her home but she was not able to hear any echo. Explain.

2.There is an explosion on the surface of a lake and two persons john and Dante hear its sound. John is 150 m away on a boat and Dante is 150 m
below the surface of water. Who would hear the sound first and why?

3.Both sound waves and light waves undergo the phenomenon of refraction
when they travel from air to water. How is refraction of sound waves different
from the refraction of light waves?

Abatter hits the baseball a with an initial velocity of v0 = 110 ft/sec directly toward fielder b at an angle of 23° to the horizontal; the initial position of the ball is 2.2 ft above ground level. fielder b requires 0.44 sec to judge where the ball should be caught and begins moving to that position with constant speed. because of great experience, fielder b chooses his running speed so that he arrives at the “catch position” simultaneously with the baseball. the catch position is the field location at which the ball altitude is 8.4 ft. determine the velocity of the ball relative to the fielder at the instant the catch is made.

Describe uniform velocity and variable velocity in short

Individuals who live below the poverty line get seriously ill more often than those who do not what could be the hidden variable in this situation?