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When a sound is reflected from a distant object, an echo is produced. Let the distance between the reflecting surface and the source of sound production remains the same. Do you hear echo sound on a hotter day?

An echo is heard when the time for the reflected sound is heard after 0.1 s Time Taken= Total Distance... View Article

When 3.0 g of carbon is burnt in 8.00 g oxygen, 11.00 g of carbon dioxide is produced. What mass of carbon dioxide will be formed when 3.00 g of carbon is burnt in 50.00 g of oxygen? Which law of chemical combinations will govern your answer?

When 3.0 g of carbon is burnt in 8.00 g oxygen, 11.00 g of carbon dioxide is produced. Given that... View Article

Two persons manage to push a motorcar of mass 1200 kg at a uniform velocity along a level road. The same motorcar can be pushed by three persons to produce an acceleration of 0.2 m s-2. With what force does each person push the motorcar? (Assume that all persons push the motorcar with the same muscular effort)

Given Mass of the motor car = 1200 kg Only two persons manage to push the car. Hence, the acceleration... View Article

The kinetic energy of an object of mass, m moving with a velocity of 5 m s^-1 is 25 J. What will be its kinetic energy when its velocity is doubled? What will be its kinetic energy when its velocity is increased three times?

Answer: We know that K.E = Kinetic energy attain by object m = Mass of the object v = Velocity... View Article

The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object? Option A: Between the principal focus and the centre of curvature Option B: At the centre of curvature Option C: Beyond the centre of curvature Option D: Between the pole of the mirror and its principal focus.

Correct Option: D Solution: Between the pole of the mirror and its principal focus. A concave mirror has a reflective... View Article

The essential difference between an AC generator and a DC generator is that A) AC generator has an electromagnet while a DC generator has permanent magnet. B) DC generator will generate a higher voltage. C) AC generator will generate a higher voltage. D) AC generator has slip rings while the DC generator has a commutator.

Answer: (D) AC generator has slip rings while the DC generator has a commutator. Generator A generator is a mechanical... View Article

Several electric bulbs designed to be used on a 220 V electric supply line, are rated 10 W. How many lamps can be connected in parallel with each other across the two wires of 220 V line if the maximum allowable current is 5 A?

Given that Electric bulbs designed to be used on a 220 V electric supply line, are rated 10 W. Find... View Article

State which of the following situations are possible and give an example for each of these: (a) an object with a constant acceleration but with zero velocity. (b) an object moving in a certain direction with acceleration in the perpendicular direction.

Answer: (a) The given statement is possible. The word acceleration implies a change in the object’s velocity. One example of... View Article

Pick out the odd property of rhombic sulphur: 1) Rhombic sulphur exists as octahedral crystals. 2) The density of rhombic sulphur is 2.06 g/mL. 3) Rhombic sulphur is yellow solid with melting point 385.8K and is soluble in carbon disulphide and insoluble in water.

Rhombic sulphur is yellow solid with melting point 385.8K and is soluble in carbon disulphide and insoluble in water.

Mountains and hills differ on the basis of: 1) A mountain is created by faulting while hill is created by either faulting or erosion. 2) A mountain is often named whereas hill is often unnamed. 3) The altitude and elevation of hill is low while the altitude and elevation of mountain is high.

1) A mountain is created by faulting while hill is created by either faulting or erosion. The faulting, that happens... View Article

Look at the activities listed below. Reason out whether work is done or not in the light of your understanding of the term ‘work’. a) Suma is swimming in a pond. b)A donkey is carrying a load on its back. c)A wind mill is lifting water from a well. d)A green plant is carrying out photosynthesis. e)An engine is pulling a train. f) Food grains are getting dried in the sun. g) A sailboat is moving due to wind energy.

Work is done whenever the given conditions are satisfied: A force acts on the body. There is a displacement of... View Article

Let the resistance of an electrical component remains constant while the potential difference across the two ends of the component decreases to half of its former value. What change will occur in the current through it?

Answer: According to Ohm’s law V = IR where V= potential difference I= Current R = Resistance We can also... View Article

Joseph jogs from one end A to the other end B of a straight 300 m road in 2 minutes 30 second and then turns around and jogs 100 m back to point C in another 1 minute. What are joseph€™s average speeds and velocities in jogging (a) from A to B and (b) from A to C?

Total Distance covered from AB = 300m Total time taken = 2—60+30s =150s Therefore, Average speed from AB= Total Distance/... View Article

(i) Straight angle (a) less than one-fourth a revolution (ii) Right angle (b) more than half a revolution (iii) Acute angle (c) half of a revolution (iv) Obtuse angle (d) one-fourth a revolution (v) Reflex angle (e) between and of a revolution (f) One complete revolution

Column A Column B (a)Straight angle 1 Less than one-fourth of a revolution (b)Right angle 2 More than half a revolution (c)Acute... View Article

Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a pendulum bob to one side and allow it to oscillate. Why does the bob eventually come to rest? What happens to its energy eventually? Is it a violation of the law of conservation of energy?

Answer: The law of conservation of energy states that energy can be neither created nor destroyed. It can only be... View Article

For the following statements, write T for True and F for False. (i) J.J. Thomson proposed that the nucleus of an atom contains only nucleons. (ii) A neutron is formed by an electron and a proton combining together. Therefore, it is neutral. (iii) The mass of an electron is about 1/2000 times that of proton. (iv) An isotope of iodine is used for making tincture iodine, which is used as a medicine.

Answer: (i) J.J. Thomson proposed that the nucleus of an atom contains only nucleons. (F) (ii) A neutron is formed... View Article

Following are some of the characteristics of animals:(i) Diets heavy on fruits (ii) White fur (iii) Need to migrate (iv) Loud voice (v) Sticky pads on feet (vi) Layer of fat under skin (vii) Wide and large paws (viii) Bright colours (ix) Strong tails (x) Long and large beak For each characteristic indicate whether it is adaptation for tropical rainforests or polar regions. Do you think that some of these characteristics can be adapted for both regions?

Adaptation is defined as the process where a species or an organism gradually becomes better acclimated to its environment. Adaptation is... View Article

Fill in the blanks: (a) A place where animals are protected in their natural habitat is called a-fill in the blank- (b) Species found only in a particular area are known as -fill in the blank- (c) Migratory birds fly to faraway places because of -fill in the blank- changes.

Solution: (a) A place where animals are protected in their natural habitat is called a sanctuary (b) Species found only in... View Article

Classify the following as chemical or physical changes: (a) Cutting of trees (b) Melting of butter in a pan (c) Rusting of almirah (d) Boiling of water to form steam (e) Passing of electric current, through water and the water breaking down into hydrogen and oxygen gases (f) Dissolving common salt in water (g) Making a fruit salad with raw fruits (h) Burning of paper and wood

Answer: Physical change – A substance is said to undergo a physical change when only the physical properties such as... View Article

Choose the odd one out for ideal gas. a) The molecules of ideal gas do not obey Newton’s laws of motion. b) An ideal gas consists of a large number of unidentical molecules. c) Ideal gases have perfectly elastic collisions. d) The molecules do not move in random motion.

Ideal gases have perfectly elastic collisions.

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