Nuclear fusion and gravitational contraction
<span>constituent of star is hydrogen(including isotope) or helium. nuclear fission is almost impossible. D(deuterium; isotope of hydrogen) and T(tritium; also isotope of hydrogen) reacts and helium is formed. During this reaction, severe energy is generated. Heavier elements are formed and pulls each other. Gathered elements forms core of star. Gravity of the core prevents the gas to run away.</span>
Will the waves bounce off each other upon meeting or will the two waves pass through each water? Waves interference occurs when two waves meet while traveling along the same medium
Answer:
c) 10.7m/s
Explanation:
From the exercise we know that at 5m the ball is traveling at 4m/s
To calculate its initial velocity we need to solve the following equation:

Since the initial height is 0
Solving for 

Sound level at distance of 15 m is given as 20 dB
so intensity at this distance is given as



now if we move closer to some some distance the sound level is now 50 dB
now the intensity is given as



now we know that



so now the distance from friend must be 47 cm