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Dorji has a few bottles of soft drink in his restaurant. But, unfortunately, these are not labelled. He has to serve the drinks on the demand of customers. One customer wants acidic drink, another wants basic and third one wants neutral drink. How will Dorji decide which drink is to be served to whom?

Answer: Dorji can detect a few drops of soft drink bottles; the acidic solution is sour, the basic solution is bitter, and the neutral solution... View Article

Draw Fig.16.6 showing the position of the plane mirror. Also, label the angle of incidence and angle of reflection on it.

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

During dry weather, clothes made of synthetic fibre often stick to the skin. Which type of force is responsible for this phenomenon?

Answer: The electrostatic force begins to work between the synthetic fibre cloth and the skin. The electrostatic force is an attractive and... View Article

During dry weather, while combing hair, sometimes we experience hair flying apart. The force responsible for this is (a) force of gravity. (b) electrostatic force. (c) the force of friction. (d) magnetic force.

Answer: (b) electrostatic force. When electric current passes through the coil, it acts as an electromagnet, producing magnetic force. The... View Article

During the construction of a building, the lightning conductor was left hanging in the air by mistake. Would the lightning conductor be still effective? Explain.

Answer: If a lightning conductor is left hanging in the air, it will not work since it must be connected to the ground with any metal (copper)... View Article

Electric current is to be passed from one body to another. For this purpose, the two bodies must be joined by (a) cotton thread (b) plastic string (c) copper wire (d) rubber band

Answer: (c) copper wire Copper is a good conductor of electricity. Plastic, rubber and cotton are bad conductors of electricity. The metals are... View Article

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Archives

Draw Fig.16.6 showing the position of the plane mirror. Also, label the angle of incidence and angle of reflection on it.

During dry weather, clothes made of synthetic fibre often stick to the skin. Which type of force is responsible for this phenomenon?

During dry weather, while combing hair, sometimes we experience hair flying apart. The force responsible for this is (a) force of gravity. (b) electrostatic force. (c) the force of friction. (d) magnetic force.

During the construction of a building, the lightning conductor was left hanging in the air by mistake. Would the lightning conductor be still effective? Explain.

Electric current is to be passed from one body to another. For this purpose, the two bodies must be joined by (a) cotton thread (b) plastic string (c) copper wire (d) rubber band

Electroplating of ______________ is done on objects like water taps and cycle bell to give them a shiny appearance.

Evaluate : (i) cos 48° – sin 42° (iii) cosec 31° – sec 59°

Evaluate : (i) sin 18°/cos 72° (ii) tan 26°/cot 64° (iii) cos 48° – sin 42° (iv) cosec 31° – sec 59°

Evaluate the following using suitable identities: (99)³

Evaluate the following: (i) sin 60° cos 30° + sin 30° cos 60°

Evaluate the following: 2 tan²45° + cos² 30° – sin² 60°

Evaluate the following: cos 45°/(sec 30° + cosec 30°)

Evaluate the products without multiplying directly: 103 × 107

Evaluate the products without multiplying directly: 104 × 96

Evaluate the products without multiplying directly: 95 × 96

Evaluate: (sin²63° + sin²27°)/(cos²17° + cos²73°)

Expand the following, using suitable identities: (- 2x + 5y – 3z)²

Expand the following, using suitable identities: (-2x + 3y + 2z)²

Expand the following, using suitable identities: (2x − y + z)²