While sewing, a person often wets the end of a thread before, trying to put it through the eye of the needle. Why?

While sewing, a person often wets the end of a thread before, trying to put it through the eys of the needle. Why?

Boojho with perfect eyesight was finding it difficult to pass a thread through the eye of a needle. What can be the possible reason for this?

Explain why (a). To keep a piece of paper horizontal, you should blow over, not under, it (b). When w try to close a water tap with our fingers, fast jets of water gush through the openings between our fingers (c). The size of the needle of a syringe controls flow rate better than the thumb pressure exerted by a doctor while administering an injection (d). A fluid flowing out of a small hole in a vessel results in a backward thrust on the vessel (e). A spinning cricket ball in air does not follow a parabolic trajectory.

It is difficult to thread a needle with one eye closed. Why?

With the help of ciliary muscles the human eye can change its curvature and thus alter the focal length of its lens. State the changes that occur in the curvature and focal length of the eye lens while viewing (a) a distance object, (b) nearby objects. Explain, why a normal eye is not able to see distincly the objects placed closer than 25 cm, without putting any strain on the eye.

Four persons went on an excursion on a hill top where temperature was quite low One of them fell sick. The other persons put a blanket on him, collect the pieces of dry wood and ignited fire in his vicinity. After sometime the sick person felt better. Read the above passage and answer the following questions: (i) What are the type of rays coming from fire? (ii) Why did the sick person feel better while seating near the fine? (iii) What basic values do you learn from this study?