Q5: Explain any two methods of Biological Manuring?
OR
Explain cross breeding of cattle with an example.
Q6: Mention the rules to be followed according to Bohr
electrons in each shell.
27: Give reasons.
a. Tides rising above the surface level of the sea.
b. Satellites can circle in a circular orbit.
c. A concert hall's ceiling is mostly curved.
Answers
Answer:
Ans 5 Two types of manure are—green manure and organic manure. Green manure is a type of cover crop grown primarily with mixing of green crop with soil. It adds nitrogen and organic matter to the soil for the improvement of crop yield. Green manuring also improves soil aeration and drainage conditions.
Ans 6 The electrons first occupy the shell with the lowest energy i.e., closest to the nucleus. The first or the innermost energy shell (K or n = 1) can take only two electrons. The second shell (L or n = 2) can contain upto 8 electrons. From third shell (M or n = 3) onwards, the shells become bigger.
Ans 27a The gravitational forces exerted by the moon and sun on the earth and also the rotation of earth is responsible for the tides. Due to the gravitational attraction the water rises above the sea level and tide is formed. When satellite moves around a planet, the gravitational force of attraction acts on it.
b satellite is an object upon which the only force is gravity. Once launched into orbit, the only force governing the motion of a satellite is the force of gravity. ... This would cause the projectile to stay the same height above the earth and to orbit in a circular path (such as path C).
c The ceiling of concert halls are curved because people seated at the back rows of the hall may not hear the sound from the speaker clearly. When the ceiling is curved or concave, it helps in reflecting sound waves making it travel to farther distances.