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You spill a bucket of soapy water on a marble floor accidently. Would it make it easier or more difficult for you to walk on the floor? Why?

It is difficult to walk because when soapy water falls on the floor then the friction between the feet and floor reduces significantly. Thus, the... View Article

Alida runs her toy car on dry marble floor, wet marble floor, newspaper and towel spread on the floor. The force of friction acting on the car on different surfaces in increasing order will be (a) wet marble floor, dry marble floor, newspaper and towel. (b) newspaper, towel, dry marble floor, wet marble floor. (c) towel, newspaper, dry marble floor, wet marble floor. (d) wet marble floor, dry marble floor, towel, newspaper

The answer is (a) wet marble floor, dry marble floor, newspaper, and towel. The force of friction depends on the nature of the surface in... View Article

Four children were asked to arrange forces due to rolling, static and sliding frictions in a decreasing order. Their arrangements are given below. Choose the correct arrangement. (a) rolling, static, sliding (b) rolling, sliding, static (c) static, sliding, rolling (d) sliding, static, rolling

The answer is option (c) Static, sliding, rolling. Sliding friction is the force of friction, below two objects, when one of them is sliding... View Article

Fill in the blanks. (a) Friction opposes the _______ between the surfaces in contact with each other. (b) Friction depends on the _ of surfaces. (c) Friction produces . (d) Sprinkling of powder on the carrom board friction. (e) Sliding friction is _______ than the static friction.

(a) Friction opposes the motion between the surfaces in contact with each other. (b) Friction depends on the irregularities of surfaces. (c)... View Article

Lightning and thunder take place in the sky at the same time and at the same distance from us. Lightning is seen earlier and thunder is heard later. Can you explain why?

Lightning is seen earlier than the thunder because speed of light is more than the speed of sound. Therefore, even though both occurs as same... View Article

Explain in what way noise pollution is harmful to human.

Noise pollution is caused in different ways. Mainly vehicles, industries are the source of noise pollution. Noise pollution can cause... View Article

List sources of noise pollution in your surroundings.

Noise is the unpleasant and undesirable sound which leads to discomfort in human beings. The intensity of sound is measured in decibels (dB).... View Article

What is the difference between noise and music? Can music become noise sometimes?

Sound is the form of energy that is produced when things vibrate. It propagates as an acoustic wave through solid, liquid and gaseous states. An... View Article

Identify the part which vibrates to produce sound in the following instruments. (a) Dholak (b) Sitar (c) Flute

(a) The vibrating part in a dholak is a stretched membrane. When the head is beaten, the stretch membrane starts vibrating gently. Thus, sound is... View Article

The sound from a mosquito is produced when it vibrates its wings at an average rate of 500 vibrations per second. What is the time period of the vibration?

Frequency equals the number of waves that passes a given point per second or the number of oscillations of a vibrating body per second or number... View Article

A pendulum oscillates 40 times in 4 seconds. Find its time period and frequency

Time period is defined as the time required to complete one oscillation. Frequency is defined as the number of oscillations per unit time. Time =... View Article

Fill in the blanks with suitable words. (a) Time taken by an object to complete one oscillation is called . (b) Loudness is determined by the of vibration. (c) The unit of frequency is (d) Unwanted sound is called . (e) The shrillness of a sound is determined by the __ of vibration.

(a) Time taken by an object to complete one oscillation is called time period. (b) Loudness is determined by amplitude of vibration. (c) The unit... View Article

In the following statements, tick ‘T’ against those which are true, and ‘F’ against those which are false. (a) Sound cannot travel in vacuum. (T/F) (b) The number of oscillations per second of a vibrating object is called its time period. (T/F) (c) If the amplitude of vibration is large, sound is feeble. (T/F) (d) For human ears, the audible range is 20 Hz to 20,000 Hz. (T/F) (e) The lower the frequency of vibration, the higher is the pitch. (T/F) (f) Unwanted or unpleasant sound is termed as music. (T/F) (g) Noise pollution may cause partial hearing impairment. (T/F)

(a) Sound cannot travel in a vacuum. (True) Explanation: Sound needs a medium to travel. (b) The number of oscillations per second of a vibrating... View Article

Voice of which of the following is likely to have a minimum frequency? (a) Baby girl (b) Baby boy (c) A man (d) A woman

Answer is: (c) The man The voice of a man is of lower pitch as compared to the voice of a baby girl, baby boy or a woman. Since frequency of... View Article

Choose the correct answer. Sound can travel through (a) gases only (b) solids only (c) liquids only (d) solids, liquids and gases

Answer is option (d) Solid, liquid and gas. Sound travels more quickly through solids than through liquids and gases because the molecules of... View Article

Two children are at opposite ends of an aluminum rod. One strikes the end of the rod with a stone. Find the ratio of times taken by the sound wave in the air and in aluminum to reach the second child.

Let the distance between the two children be d Also let the time taken by sound to reach other child via air be t1 and via aluminium rod be t2.... View Article

Flash and thunder are produced simultaneously. But thunder is heard a few seconds after the flash is seen, why?

Thunder is heard few seconds later after the flash because speed of light in atmosphere for air is 3 × 108 ms-2which is very high, as... View Article

A person is listening to a tone of 500 Hz sitting at a distance of 450 m from the source of the sound. What is the time interval between successive compressions from the source?

Given - n=500Hz the time interval between two successive compressions or rarefactions is called, time period of wave, which is given by , T = 1/n... View Article

Which wave property determines (a) loudness, (b) pitch?

(a) The loudness or softness of a sound is determined by its amplitude. (b) Pitch of the sound is determined by its frequency. The pitch of a... View Article

What are the immunization programs available at the nearest health center in your locality? Which of these diseases are the major health problems in your area?

A process by which a person becomes protected against a disease through vaccination. Immunity (protection) by immunization is similar to the... View Article

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