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To clean their spectacles, people often breathe out on glasses to make them wet. Explain why the glasses become wet.

The gases that we breathe our contain water vapour which condenses at spectacles. So, the glass becomes wet and with the help of small... View Article

Water vapour condenses to form tiny droplets of water in the upper layers of air where it is cooler. (True or False)

True The water vapour condenses to form tiny droplets of water in the upper layers of air, where it is cooled and forms clouds. Condensation in... View Article

Write the similarities and differences between the motion of a bicycle and a ceiling fan that has been switched on.

(i) The blades of the fan and the wheels of the bicycle are in a circular motion. (ii) The blades of the fan and spokes of the wheels of the... View Article

Normal range of breathing rate per minute in an average adult person at rest is: (i) 9–12 (ii) 15–18 (iii) 21–24 (iv) 30–33

Normal range of breathing rate per minute in an average adult person at rest is (ii) 15–18. Breathing (or ventilation) is the process of... View Article

Given below is a sequence of steps in the processing of wool. Which are the missing steps? Add them. Shearing, __, sorting, , , _.

Shearing, Scouring, sorting, Cleaning of burrs, Dyeing, Rolling. The various steps for processing fibres into wool are as follows: Shearing:... View Article

The angle of incidence is equal to the angle of reflection. (a) Always (b) Sometimes (c) Under special conditions (d) Never

Answer: (a) Always, the Angle of incidence is equal to the angle of reflection. When light is reflected from a surface, the angle of incidence... View Article

Which of the following is NOT a member of the solar system? (a) An asteroid (b) A satellite (c) A constellation (d) A comet

Answer: (c) A Constellation. A constellation is a group of stars forming a recognizable shape. A constellation is a group of stars that... View Article

Why do farmers grow many fruits and vegetable crops inside large greenhouses? What are the advantages to the farmers?

Greenhouse provides favourable conditions for many fruits and vegetable crops like it always gives favourable temperature heat, light etc . for... View Article

Mark ‘T’ if the statement is true and ‘F’ if it is false: During heavy exercise the breathing rate of a person slows down.

During heavy exercise, the breathing rate of a person slows down. (False) Breathing rates may increase from a normal resting rate of 15 breaths... View Article

How can you contribute to the maintenance of green wealth of your locality? Make a list of actions to be taken by you.

The green wealth of the locality is the responsibility of every resident. Green wealth refers to the forests, vegetation that we have in our... View Article

A bar magnet has no markings to indicate its poles. How would you find out near which end is its north pole is located?

The location of the poles of the magnet can be determined by suspending it freely. A freely suspended bar magnet always points in a north-south... View Article

In a completely dark room, if you hold up a mirror in front of you, will you see a reflection of yourself in the mirror?

No, we will not see our reflection in a mirror in a dark room because an image is formed only when the light gets reflected by the mirror whereas... View Article

You accidentally dropped your favorite toy and broke it. This is a change you did not want. Can this change be reversed?

No, this change cannot be reversed. Though this is an irreversible change, but it did not cause any change in the composition of the toy. This... View Article

To walk through a waterlogged area, you usually shorten the length of your dress by folding it. Can this change be reversed?

Yes, this change can be reversed by unfolding the dress. A change which can happen backward, that is, can be reversed is called a reversible... View Article

The transfer of pollen grains from the anther to the stigma of the same or of another flower of the same kind is known as _____________.

The transfer of pollen grains from the anther to the stigma of the same or of another flower of the same kind is known as pollination. Transfer... View Article

The distance between two stations is 240 km. A train takes 4 hours to cover this distance. Calculate the speed of the train.

Given that, Distance of two stations = 240 km Time taken by the train = 4 hours The equation of speed is given as Speed = (Distance travelled) /... View Article

Make sketches of the two stages in the life history of the silk moth which are directly related to the production of silk.

The egg is laid by a female moth, which is mostly the size of small dots. A female moth lays more than 350 eggs at a time. In the springtime,... View Article

Differentiate between regular and diffused reflection. Does diffused reflection mean the failure of the laws of reflection?

When all the parallel rays reflected from a plane surface are not parallel, the reflection is known as diffused or irregular reflection.... View Article

A blacksmith hammers a hot piece of iron while making a tool. How does the force due to hammering affect the piece of iron?

When the iron is heated it gets softened. A blacksmith hammers on the hot iron, he applies force. This applied force changes the shape of iron.... View Article

Which of the things in the following list are nonliving? Plough, Mushroom, Sewing machine, Radio, Boat, Water hyacinth, Earthworm

Non-living things are plough, sewing machine, radio, and boat. On the other hand, mushrooms, water hyacinth, and earthworms are living things.... View Article

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