Archives

If tan (A + B) = √3 and tan (A – B) = 1/√3 ,0° < A + B ≤ 90°; A > B, find A and B.

Answer: Trigonometry values for angles 0°, 30°, 45°, 60°and 90°, with respect to sin, cos, tan, cot, sec, cosec functions,... View Article

If tan 2A = cot (A – 18°), where 2A is an acute angle, find the value of A.

Answer: An angle that is measuring less than 90 degrees is called an acute angle. This angle is smaller than the right angle (which is equal to... View Article

If tan A = cot B, prove that A + B = 90°.

Answer: tan A = cot B We know that cot B = tan (90° – B) To prove A + B = 90°, substitute the above equation in the given problem tan A = tan... View Article

If the materials used for constructing a building were good conductors, do you think lightning will strike the building? Will the lightning conductor be still required to be installed in the building?

Answer: Because charge separation cannot occur in conductors, lightning will not impact the building and any lightning that strikes it will fall... View Article

If the metal clip used in the electroscope is replaced by an ebonite rod and a charged body is brought in contact with it, will there be any effect on the aluminium strips? Explain.

Answer: There will be no repellent effect between the aluminium strips. Because the ebonite rod is an insulator, the charged body will not... View Article

If we apply oil on door hinges, the friction will (a) increases (b) decreases (c) disappear altogether (d) will remain unchanged

Answer: (b) decreases Friction will be reduced as oil acts as a lubricant, reducing friction. When the surface of one object comes into touch... View Article

If x + y + z = 0, show that x³ + y³ + z³ = 3xyz.

Answer: We know that x3 + y3 + z3 - 3xyz = (x + y + z)(x2 + y2 + z2 - xy - yz - xz) Now, according to the question, let (x + y + z) = 0, then,... View Article

If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the ___________terminal of the battery.

Answer: If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the negative Electroplating is a... View Article

Imagine that an object is falling through a long straight glass tube held vertical; the air has been removed completely from the tube. The object does not touch the walls of the tube. Will the object experience any force of friction?

Answer: No, the object will not be subjected to any frictional force since the force of friction requires two surfaces, and there is only one in... View Article

In ∆ ABC, right-angled at B, AB = 24 cm, BC = 7 cm. Determine: (i) sin A, cos A (ii) sin C, cos C

Answer: In a given triangle ABC, right-angled at B = ∠B = 90° Given AB = 24 cm BC = 7 cm According to the Pythagoras Theorem, in a... View Article

In ∆ PQR, right-angled at Q, PR + QR = 25 cm and PQ = 5 cm. Determine the values of sin P, cos P and tan P

Answer: In a given triangle PQR, right angled at Q, the following measures are PQ = 5 cm PR + QR = 25 cm Now let us assume, QR = x PR = 25 -... View Article

In a large commercial complex, there are four ways to reach the main road. One of the paths has loose soil, the second is laid with polished marble, the third is laid with bricks and the fourth has a gravel surface. It is raining heavily and Paheli wishes to reach the main road. The path on which she is least likely to slip is (a) loose soil. (b) polished marble. (c) bricks. (d) gravel.

Answer: (d) gravel She should use a gravel surface path because only in this path. She will have sufficient friction force to walk easily.... View Article

In an electroscope, if a negatively charged body is brought in contact with the metal clip, the strips of the electroscope diverge. If now another charged object carrying an equal amount of positive charge is brought in contact with the clip, what will happen?

Answer: If the clip of the electroscopic gets in contact with the positively charged object then negatively charged provided earlier will get... View Article

In case of a fire, before the firemen use the water hoses, they shut off the main electrical supply for the area. Explain why they do this.

Answer: Because water in water hoses contains salts, it is an excellent conductor of electricity. If the area's electrical supply isn't turned... View Article

In Fig, two boys A and B are shown applying force on a block. If the block moves towards the right, which one of the following statements is correct? (a) The magnitude of force applied by A is greater than that of B. (b) The magnitude of force applied by A is smaller than that of B. (c) The net force on the block is towards A. (d) The magnitude of force applied by A is equal to that of B.

Answer: (a) Magnitude of force applied by A is greater than that of B. When force is applied to a stationary object, the object tends to move in... View Article

In Fig. mark the arrows (←), (→), (↓), or (↑) to show the direction of sunlight

Answer: The Earth's day and night are determined by the Sun's position. The day will be on the side of the Earth-facing the Sun, while the other... View Article

In Fig., a boy is shown pushing the box from right to left. The force of friction will act on the box (a) from right to left (←) (b) from left to right (→) (c) vertically downwards (↓) (d) vertically upwards (↑)

Answer: (b) from left to right (→) When the surface of one object comes into touch with the surface of another, friction is the force... View Article

In order to reduce the loudness of a sound, we have to (a) decrease its frequency of vibration of the sound. (b) increase its frequency of vibration of the sound. (c) decrease its amplitude of vibration of the sound. (d) increase its amplitude of vibration of the sound.

Answer: (c) decrease its amplitude of vibration of the sound. Sound is directly proportional to the loudness of sound. As a result by decreasing... View Article

In the circuit given as Fig. , Boojho observed that copper is deposited on the electrode connected to the negative terminal of the battery. Paheli tried to repeat the same experiment. But she could find only one copper plate. Therefore she took a carbon rod as a negative electrode. Will copper be still deposited on the carbon rod? Explain your answer.

Answer: Copper will be deposited on the carbon rod from the copper sulphate solution. When an electric current is passed through a copper... View Article

In the circuit shown in Fig., when the circuit is completed, the hammer strikes the gong. Which of the following force is responsible for the movement of the hammer? (a) gravitational force alone (b) electrostatic force alone (c) magnetic force alone (d) frictional force alone

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

M	T	W	T	F	S	S
			1	2	3	4
5	6	7	8	9	10	11
12	13	14	15	16	17	18
19	20	21	22	23	24	25
26	27	28	29	30	31