Crop Production and Management — Science STD 8 — Question

Why does the increased level of nutrients in the water affect the survival of aquatic organisms?

The frictional force between two moving surfaces which are in contact with each other is called kinetic friction or sliding friction.
Example If a boy apply some pushing force on the box, the box will start sliding on the surface and the friction between the surfaces is called sliding friction.
The force required to keep a body in motion is less than the force required to start the motion, so we can say that sliding friction is less than the static friction.

(i) Explain why the sliding friction is always greater than rolling friction?
(ii) Mention two different examples for sliding friction.

Given below is a conversation between two farmers Heera and Beera.
Heera: Brother Beera, your maize crops look beautiful. They have grown pretty fast.
Beera: Yes, I have sprayed urea this time. What about you ?
Heera: Well, I am still relying on good old cow dung. I am saving money for buying a tractor.
Beera: That's good. Tractor saves a lot of time and labour.
Heera: Yes, it's been very labour intensive for me and now these weeds have come up.
Beera: Try weedicides, they are very effective.
Now, answer the following questions.
(i) List the practices which are not environment friendly and why ?
(ii) What is the advantage of modern agricultural Implements over traditional ones ?
(iii) Name one weedicide and the precaution, farmers must take during its application.

Observe the set-up given in Figure and answer the following questions.

Q.1. What happens to the sugar solution in flask A?
Q.2. What do you observe in test tube B after four hours? Why do you think this happened?
Q.3. What would happen if yeast were not added to flask A?

What is meant by an ‘embryo’? Can we identify the body features in an embryo?

By taking the example of snakes, explain how by killing small animals, we are actually harming ourselves.

Why should paper be saved? Prepare a list of ways by which you can save paper.

What precautions would you take to protect yourself during an earthquake if you are inside the house?

Draw a labeled diagram of the human male reproductive system.

Analyze the impact of the Odisha community sanitation campaign and suggest similar initiatives for your area.