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Paheli wants to deposit silver on an iron spoon. She took a silver nitrate (AgNO³) solution in a beaker and set up a simple circuit for electroplating. Which terminal of the battery should the spoon be connected to? What material should the other electrode be made of?

Answer: The spoon should be connected to the negative terminal of the battery. The other electrode should be made of silver. Electroplating is... View Article

Part of the eye which controls the light entering is called (a) iris (b) cornea (c) lens (d) retina

Answer: (a) Iris Iris a dark muscular tissue and ring-like structure behind the cornea are known as the iris. The colour of the iris actually... View Article

Pitch of sound is determined by its (a) frequency (b) amplitude (c) speed (d) loudness

Answer: (a) frequency The Pitch of the sound depends on the frequency of vibration of the waves. The sound is loud and has a high pitch if the... View Article

Plastic straws A and B are rubbed with a dry cotton cloth. What will happen if they are brought near each other?

Answer: They will repel each other because when the plastic straws are rubbed with the cotton cloth, they both acquire the same charge, and like... View Article

Prepare a list of objects around you that are electroplated.

Answer: Electroplating is a process that uses an electric current to reduce dissolved metal cations so that they form a thin coherent metal... View Article

Prove the following identities, where the angles involved are acute angles for which the expressions are defined. (i) (1 + sec A)/sec A = sin²A/(1-cos A) [Hint: Simplify LHS and RHS separately] (ii) (cos A–sin A+1)/( cos A +sin A–1) = cosec A + cot A, using the identity cosec²A = 1+cot²A.

Answer: (i) (1 + sec A)/sec A = sin2A/(1-cos A) First find the simplified form of L.H.S L.H.S. = (1 + sec A)/sec A Since secant function is... View Article

Prove the following identities, where the angles involved are acute angles for which the expressions are defined. (i) (cosec θ – cot θ)2 = (1-cos θ)/(1+cos θ) (ii) cos A/(1+sin A) + (1+sin A)/cos A = 2 sec A (iii) tan θ/(1-cot θ) + cot θ/(1-tan θ) = 1 + sec θ cosec θ [Hint : Write the expression in terms of sin θ and cos θ]

Answer: To prove this, first take the Left-Hand side (L.H.S) of the given equation, to prove the Right Hand Side (R.H.S) L.H.S. = (cosec... View Article

Prove the following identities, where the angles involved are acute angles for which the expressions are defined. (i) (sin θ – 2sin3θ)/(2cos3θ-cos θ) = tan θ (ii) (sin A + cosec A)² + (cos A + sec A)² = 7 + tan²A + cot²A (iii) (cosec A – sin A)(sec A – cos A) = 1/(tan A+cotA) [Hint : Simplify LHS and RHS separately]

Answer: L.H.S. = (sin θ – 2sin3θ)/(2cos3θ – cos θ) Take sin θ as in numerator and cos θ in... View Article

Prove the following identities, where the angles involved are acute angles for which the expressions are defined. (i) √(1+sin A)/(1-sin A) = sec A + tan A (ii) (1+tan²A/1+cot²A) = (1-tan A/1-cot A)² = tan²A

Answer: sec2A + tan2A = 1 ⇒ sec A + tan A = R.H.S L.H.S. = (1+tan2A/1+cot2A) Since cot function is the inverse of tan function, = (1 +... View Article

Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from synthetic material? Advise Rana, giving your reason.

Answer: For the summer, Rana should buy a cotton shirt rather than a synthetic shirt. Cotton is a good water absorbent. So that it can absorb and... View Article

Represent -2/11, -5/11, -9/11 on a number line.

Answer: A number line is a pictorial representation of numbers on a straight line. It’s a reference for comparing and ordering numbers. It can... View Article

Represent the numbers on the number line. -5/6

Answer: A number line is a pictorial representation of numbers on a straight line. It’s a reference for comparing and ordering numbers. It... View Article

Saloni took a piece of burning charcoal and collected the gas evolved in a test tube. (a) How will she find the nature of the gas? (b) Write down word equations of all the reactions taking place in this process.

Answer: (a) In the test tube where the gas is collected, Saloni needs to add some water. She must cover the tube and shake it vigorously. She'll... View Article

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Archives

Paheli wants to deposit silver on an iron spoon. She took a silver nitrate (AgNO³) solution in a beaker and set up a simple circuit for electroplating. Which terminal of the battery should the spoon be connected to? What material should the other electrode be made of?

Part of the eye which controls the light entering is called (a) iris (b) cornea (c) lens (d) retina

Pitch of sound is determined by its (a) frequency (b) amplitude (c) speed (d) loudness

Plastic straws A and B are rubbed with a dry cotton cloth. What will happen if they are brought near each other?

Prepare a list of objects around you that are electroplated.

Prove the following identities, where the angles involved are acute angles for which the expressions are defined. (i) (1 + sec A)/sec A = sin²A/(1-cos A) [Hint: Simplify LHS and RHS separately] (ii) (cos A–sin A+1)/( cos A +sin A–1) = cosec A + cot A, using the identity cosec²A = 1+cot²A.

Prove the following identities, where the angles involved are acute angles for which the expressions are defined. (i) √(1+sin A)/(1-sin A) = sec A + tan A (ii) (1+tan²A/1+cot²A) = (1-tan A/1-cot A)² = tan²A

Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from synthetic material? Advise Rana, giving your reason.

Represent -2/11, -5/11, -9/11 on a number line.

Represent the numbers on the number line. -5/6

Saloni took a piece of burning charcoal and collected the gas evolved in a test tube. (a) How will she find the nature of the gas? (b) Write down word equations of all the reactions taking place in this process.

Should the handle and bristles of a tooth brush be made of the same material? Explain your answer

Show that: (3x + 7)² – 84x = (3x – 7)²

Show that: (4pq + 3q)² – (4pq – 3q)² = 48pq²

Show that: (9p – 5q)² + 180pq = (9p + 5q)²

Show that: (a – b)(a + b) + (b – c)(b + c) + (c – a) (c + a) = 0

Show that: cos 38° cos 52° – sin 38° sin 52° = 0

Show that: tan 48° tan 23° tan 42° tan 67° = 1

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