B) Acceleration is directly proportional to the mass of the object
Answer: Elastic Potential Energy
Explanation: Energy present on compressed strings is called Elastic Potential Energy.
This question involves the use of the equations of motion for vertical motion.
The time taken by the stones P and Q to reach the ground is the same, that is "2 s".
The velocity with which Q hits the ground is "20 m/s".
The time taken by the stones to reach the ground can be calculated by using the second equation of motion for the vertical motion:

For both the stones P and Q:
h = height = 20 m
= initial velocity = 0 m/s
t = time = ?
g = acceleration due to gravity = 10 m/s²
Therefore,

<u>t = 2 s</u>
<u></u>
Hence, the time taken by both the stones to reach the ground <u>is the same</u>.
To find the final velocity of stone Q we will use the first equation of motion for the vertical motion:

Learn more about equations of motion here:
brainly.com/question/20594939?referrer=searchResults
The attached picture shows the equations of motion in the horizontal and vertical directions.
Speed of sound through a medium depends on
● temperature
● density of medium
● speed of wind
● humidy
● moisture
Speed of sound increases with increase in temperature. Because when temperature increases the molecules get higher energy and they vibrate quickly. Due to this vibration sound waves can travel fastly.