a) Explain how deforestation leads to global warming?
b) Suitcases and trunks are widely replaced by the trolley bags to carry cloths and other essential things in journey. Why people prefer trolley bags over suitcases?
c) Explain why is it easier to move an object further which is already moving than the object at rest, and it is even easier to move an object with wheels?
d) Explain the process of formation of petroleum.
e) Milu visited a granary recently. When he observed the sacks of the grains he found leaves of Indian Lilac (Neem leaves) in some
of them and small packets of chemicals inside it. Why do you think the leaves or the chemicals packets are kept in the grain sacks?
What are the other process followed before storing the harvested grains?
f) Your uncle has 20 acres of agricultural field. He wanted to restore the nutrients of the soil to increase the production, but he is confused whether to use Manures or Fertilizers. What would you advise him ? Justify your point
g) Though plastics are very useful, their use is always restricted. Why do you think so? Can you suggest some ways to reduce the
use of plastics?
Answers
(a) When trees are cut down and burned or allowed to rot, their stored carbon is released into the air as carbon dioxide. And this is how deforestation and forest degradation contribute to global warming.
(b) When one body rolls over the surface of another body, the resistance to its motion is Dalled the rolling friction. Rolling reduces friction. It is always easier to roll than to slide a body over another. That is the reason it is convenient to pull the luggages fitted with rollers.
(c) It is easy to move an object already in motion than when it is at rest.... because of friction the object sticks to its surface... This energy is in addition to the energy that it takes to accelerate the object..... A moving object has already overcome this additional energy
(d) A fossil fuel, petroleum is formed when large quantities of dead organisms, mostly zooplankton and algae, are buried underneath sedimentary rock and subjected to both intense heat and pressure. Petroleum has mostly been recovered by oil drilling (natural petroleum springs are rare).
(e) Harvested grains are usually dried before being stored because moisture encourages the growth of microorganisms. They are then stored in metal or earthen containers, gunny bags or grain silos. The godowns where grains are stored are first fumigated to get rid of pests.