Archives

It is much easier to burst an inflated balloon with a needle than by a finger. Explain.

Answer: Because the needle tip has a much smaller cross-section than our finger, and we know that pressure imposed by a force is inversely... View Article

John saw the full moon on a particular day. After how many days will he be able to see the full moon again?

Answer: A lunar cycle is completed in a month that is the size of the moon from zero to the full moon stage and back to. If John sees a full moon... View Article

Light is falling on surface S1, S2, S3 as shown in Fig.. Surfaces on which the angle of incidence is equal to the angle of reflection is/are (a) S1 only (b) S1 and S2 only (c) S2 and S3 (d) all the three surfaces

Answer: (d) all the three surfaces Laws of reflection are always followed irrespective of the surface of the object hence the angle of... View Article

Lightning can be seen as the moment it occurs. Paheli observes lightning in her area. She hears the sound 5 s after she observed lightning. How far is she from the place where lightning occurs? (speed of sound = 330 m/s).

Answer: 1650m Sound travels at a significantly slower rate than light. Sound travels at a speed of around 340 metres per second in air. Light... View Article

List three states in India where earthquakes are more likely to strike.

Answer: Gujarat, Assam and Jammu & Kashmir are the three states where an earthquake is more likely to strike. An earthquake zone is... View Article

Look at Fig. Can the image of the child in it be obtained on a screen?

Answer: Because the image of the child is not real, it cannot be obtained on the screen. Because the images formed by a plane mirror are... View Article

Look at Fig. carefully and answer the following question: (a) In which part of the sky would you see the full moon in the evening? (b) In which part of the sky would you see the crescent moon in the evening?

Answer: We see the full moon in the evening in the eastern part of the sky. Full moon - The full moon is one of the phases of the moon when... View Article

Major earthquakes are less likely to occur in (a) North East India (b) Rajasthan (c) Rann of Kutch (d) Orissa

Answer: (d) Orissa In Orissa, major earthquakes are less likely to occur. Kashmir, the Western and Central Himalayas, the entire North-East, the... View Article

Mark ‘T’ if the statement is true and ‘F’ if it is false: (i) Indicator is a substance which shows different colours in acidic and basic solutions. (T/F) (ii) Tooth decay is caused by the presence of a base. (T/F)

Answer: (i) Indicator is a substance which shows different colours in acidic and basic solutions - True (T) Acidic and basic substances abound in... View Article

Mark ‘T’ if the statement is true and ‘F’ if it is false: (i) Nitric acid turn red litmus blue. (T/F) (ii) Sodium hydroxide turns blue litmus red. (T/F) (iii) Sodium hydroxide and hydrochloric acid neutralise each other and form salt and water. (T/F) (iv) Indicator is a substance which shows different colours in acidic and basic solutions. (T/F) (v) Tooth decay is caused by the presence of a base. (T/F)

Answer: (i) Nitric acid turn red litmus blue - False(F) Nitric acid does not turn the red litmus paper into the blue. The explanation is that the... View Article

Mark ‘T’ if the statement is true and ‘F’ if it is false. (a) Generally, non-metals react with acids. ( ) (b) Sodium is a very reactive metal. ( ) (c) Copper displaces zinc from zinc sulphate solution. ( ) (d) Coal can be drawn into wires. ( )

Answer: (a) Generally, non-metals react with acids. (False) Non-metal substances, in general, do not react with acids. When a substance reacts... View Article

Mark the correct answer. Rayon is different from synthetic fibres because (a) it has a silk-like appearance. (b) it is obtained from wood pulp. (c) its fibres can also be woven like those of natural fibres.

Answer: (b) it is obtained from wood pulp. Synthetic fibres are manmade fibres that have been prepared with chemicals. They're made up of small... View Article

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Archives

It is much easier to burst an inflated balloon with a needle than by a finger. Explain.

John saw the full moon on a particular day. After how many days will he be able to see the full moon again?

Light is falling on surface S1, S2, S3 as shown in Fig.. Surfaces on which the angle of incidence is equal to the angle of reflection is/are (a) S1 only (b) S1 and S2 only (c) S2 and S3 (d) all the three surfaces

Lightning can be seen as the moment it occurs. Paheli observes lightning in her area. She hears the sound 5 s after she observed lightning. How far is she from the place where lightning occurs? (speed of sound = 330 m/s).

List three states in India where earthquakes are more likely to strike.

Look at Fig. Can the image of the child in it be obtained on a screen?

Look at Fig. carefully and answer the following question: (a) In which part of the sky would you see the full moon in the evening? (b) In which part of the sky would you see the crescent moon in the evening?

Major earthquakes are less likely to occur in (a) North East India (b) Rajasthan (c) Rann of Kutch (d) Orissa

Mark ‘T’ if the statement is true and ‘F’ if it is false: (i) Indicator is a substance which shows different colours in acidic and basic solutions. (T/F) (ii) Tooth decay is caused by the presence of a base. (T/F)

Mark ‘T’ if the statement is true and ‘F’ if it is false. (a) Generally, non-metals react with acids. ( ) (b) Sodium is a very reactive metal. ( ) (c) Copper displaces zinc from zinc sulphate solution. ( ) (d) Coal can be drawn into wires. ( )

Mark the correct answer. Rayon is different from synthetic fibres because (a) it has a silk-like appearance. (b) it is obtained from wood pulp. (c) its fibres can also be woven like those of natural fibres.

Mass of one atom of oxygen is(a) 16 / 6.023 ×10²³ g (b) 32 / 6.023 ×10 ²³ g (c) 1 / 6.023× 10²³ g (d) 8u

Mention three precautions that you will take to protect yourself if an earthquake strikes when you are inside the house.

Meteors are not visible during the daytime. Explain the reason.

Micro-organisms act upon the dead plants to produce (i) sand (ii) mushrooms (iii) humus (iv) wood

Morning star is the name given to (a) pole star (b) star Sirius (c) planet Jupiter (d) planet Venus

Most liquids that conduct electricity are solutions of , and .

Multiply 6/13 by the reciprocal of -7/16

Multiply the binomials: (2.5l – 0.5m) and (2.5l + 0.5m)