Question 71 : Sound of frequency below 20 Hz is called
1. audio sounds
2. infrasonic
3. ultrasonic
4. supersonics
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Question 72 : Planets are
1. luminous heavenly bodies revolving around a star
2. non-luminous heavenly bodies
3. luminous heavenly bodies that twinkle
4. luminous heavenly bodies that do not twinkle
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Question 73 : It is more difficult to walk on a sandy road than on a concrete road because
1. sand is soft and concreter is hard
2. the friction between sand and feet is less than that between concrete and feet
3. the friction between sand and feet is more than that between concrete and feet
4. the sand is grainy but concrete is smooth
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Question 74 : It is easier to roll a barrel full of coal tar than to pull it because
1. the full weight of the barrel comes into play when it is pulled
2. the rolling friction is much less than the sliding friction
3. more surface area of the barrel is in contact with the road when it is pulled
4. coal tar is a liquid and it flows in the barrel when it is rolled
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Question 75 : One watt-hour is equivalent to
1. 6.3 x 10³ J
2. 6.3 x 10^-7 J
3. 3.6 x 10³ J
4. 3.6 x 10^-3 J
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Question 76 : Lux is the SI unit of
1. intensity of illumination
2. luminous efficiency
3. luminous flux
4. luminous intensity
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Question 77 : An atom with more neutrons than protons is called
1. Compound
2. Element
3. Isotope
4. None of the above
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Question 78 : Charles's law is based on
1. Solid
2. Liquid
3. Gas
4. None of the above
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Question 79 : The SI unit for measuring work and energy is
1. Joule
2. Watt
3. Farad
4. Ohm
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Question 80 : Infrasonic sound has a frequency lower than
1. 5 Hz
2. 15 Hz
3. 20 Hz
4. 32 Hz
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