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The weather department has predicted that a thunderstorm is likely to occur on a certain day. Suppose you have to go out on that day. Would you carry an umbrella? Explain.

Answer: In a thunderstorm, we should not bring an umbrella because thunderstorms are usually accompanied by lightning. During lightning,... View Article

There is a mistake in each of the following ray diagrams given as Fig. a, b, and c. Make the necessary correction (s).

Answer: The angle of incidence is equal to the reflected angle through the law of reflection. The angle of incidence and the angle of... View Article

Three liquids are given to you. One is hydrochloric acid, another is sodium hydroxide and third is a sugar solution. How will you identify them? You have only turmeric indicator.

Answer: The following steps are taken to test the given liquids: Put a drop of provided liquid on the turmeric indicator. The solution that... View Article

To sharpen the blade of a knife by rubbing it against a surface, which of the following will be most suitable? (a) stone (b) plastic block (c) wooden block (d) glass block

Answer: (a) stone The stone will be more suitable since it will provide a greater reaction and hence a higher friction force, allowing the blade... View Article

Tremors on the earth can also be caused by the eruption of a volcano. (True & False)

Answer: True A volcano is a landform, a mountain, where molten rocks erupt through the surface of the planet. The volcano mountain opens... View Article

Two astronauts are floating close to each other in space. Can they talk to each other without using any special device? Give reasons.

Answer: In space, there will be no medium for sound waves to travel through, only vacuum. Because sound cannot travel through vacuum, it must... View Article

Two blocks of iron of different masses are kept on a cemented floor as shown in Fig.12.2. Which one of them would require a larger force to move it from the rest position?

Answer: A larger force will be required to move the heavier block. Because the force of friction increases as the mass of the object... View Article

Two boys are riding their bicycles on the same concrete road. One has new tyres on his bicycle while the other has tyres that are old and used. Which of them is more likely to skid while moving through a patch of the road which has lubricating oil spilt over it?

Answer: The boy with the old and worn tyres is more likely to slip since the tyres will have less friction force, which will be insufficient to... View Article

Two charged objects are brought close to each other. Choose the most appropriate statement from the following options: (a) they may attract (b) they may repel (c) they may attract or repel depending on the type of charges they carry (d) there will be no effect

Answer: (c) they may attract or repel depending on the type of charges they carry If the charges are like, they repel each other, and if they are... View Article

Two methods by which rusting of iron can be prevented are _ and _.

Answer: Two methods by which rusting of iron can be prevented are painting and galvanization. Rusting of iron refers to the formation of rust, a... View Article

Two mirrors A and B are placed at right angles to each other as shown in Fig.. A ray of light incident on mirror A at an angle of 250 falls on mirror B after reflection. The angle of reflection for the ray reflected from mirror B would be (a) 250 (b) 500 (c) 650 (d) 1150

Answer: (c) 650 In case of a plane mirror the ray of light after reflection follows the laws of reflection. The first law of reflection states... View Article

Two objects repel each other. This repulsion could be due to (a) frictional force only (b) electrostatic force only (c) magnetic force only (d) either a magnetic or an electrostatic force

Answer: (d) either a magnetic or an electrostatic force When there is a repulsive force between two objects, it could be due to an electrostatic... View Article

Two persons are applying forces on two opposite sides of a moving cart. The cart still moves with the same speed in the same direction. What do you infer about the magnitudes and direction of the forces applied?

Answer: The magnitude of the forces will be equal, and they will act in opposing directions, cancelling each other out. Force applied is of equal... View Article

Two rods of the same weight and equal length have different thickness. They are held vertically on the surface of sand as shown in Fig. Which one of them will sink move? Why?

Answer: The area where force is applied is inversely proportional to the pressure exerted by the body. As a result, the thinner rod, i.e. rod B... View Article

Two women are of the same weight. One wears sandals with pointed heels while the other wears sandals with flat soles. Which one would feel more comfortable while walking on a sandy beach? Give reasons for your answer.

Answer: Women are the same height and walk with the same weight. Women wearing flat-heeled sandals, will be more comfortable walking on a sandy... View Article

Ultrasound has a frequency of vibration (a) between 20 and 20,000 Hz (b) below 20 Hz (c) above 20,000 Hz (d) between 500 and 10,000 Hz

Answer: (c) above 20,000 Hz Sound waves with frequencies higher than the upper audible limit of human hearing are called ultrasound. The limit... View Article

Untreated human excreta is a health hazard. Explain

Answer: Excretion is the process through which metabolic wastes are ejected from an organism in biology. This process is typically carried out by... View Article

Use a suitable identity to get each of the following products. (i) (3a – 1/2)(3a – 1/2) (ii) (1.1m – 0.4) (1.1m + 0.4) (iii) (a²+ b²) (- a² + b²)

Answer: (3a - 1/2)(3a - 1/2) = (3a - 1/2)2 Using the identity (a - b)2= a2 + b2 - 2ab (3a - 1/2)2 = 9a2 + (1/4) - 3a Using the identity (a... View Article

Use a suitable identity to get each of the following products. (i) (6x – 7) (6x + 7) (ii) (- a + c) (- a + c) (iii) (1/2x + 3/4y) (1/2x + 3/4y) (iv) (7a – 9b) (7a – 9b)

Answer: (6x - 7)(6x + 7) Using the identity (a - b)(a + b) = a2 - b2 (6x - 7)(6x + 7) = 36x2 - 49 Using the identity (a - b)2 = a2 + b2 -... View Article

Use a suitable identity to get each of the following products. (i) (x + 3) (x + 3) (ii) (2y + 5) (2y + 5) (iii) (2a – 7) (2a – 7)

Answer: (x + 3)(x + 3) = (x + 3)2 Using Using the identity (a + b) 2 = a2 + b2 + 2ab (x + 3)2 = x2 + 6x + 9 (2y + 5) (2y + 5) = (2y + 5)2... View Article

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