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... View Article
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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... 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... 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... 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. Earthquake... 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... 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: (a) In which part of the sky would you see the full moon in the evening? We see the... 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... 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... 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... 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... 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... View Article
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
Answer: (a) 16/6.023 × 1023 g The molecular mass of an element is defined as the sum of the masses... View Article
Mention three precautions that you will take to protect yourself if an earthquake strikes when you are inside the house.
Answer: An earthquake is the shaking of the surface of Earth due to the sudden release of energy in the... View Article
Meteors are not visible during the daytime. Explain the reason.
Answer: Meteors are very small objects that light as they enter the earth’s atmosphere owing to friction. Because their brightness... View Article
Micro-organisms act upon the dead plants to produce (i) sand (ii) mushrooms (iii) humus (iv) wood
Answer: (iii) humus Microorganisms break down dead plants to make humus. Many microorganisms, such as algae and amoeba, decompose various... View Article
Morning star is the name given to (a) pole star (b) star Sirius (c) planet Jupiter (d) planet Venus
Answer: (d) planet Venus Venus Venus is the second planet from the Sun and is the brightest planet in the... View Article
Most liquids that conduct electricity are solutions of , ______________ and ______________.
Answer: Most liquids that conduct electricity are solutions of acids, bases and salts. Why do some solutions conduct electricity? When... View Article
Multiply 6/13 by the reciprocal of -7/16
Answer: – 96/91 The multiplicative inverse of a number N is represented by 1/N or N-1. It is also called... View Article
Multiply the binomials: (2.5l – 0.5m) and (2.5l + 0.5m)
Answer: 6.25 l2 – 0.25 m2 Polynomials are algebraic expressions that consist of variables and coefficients. Polynomials are of 3... View Article
