Physics miscellaneous
- The intensity ratio of waves is 25 : 9. What is the ratio of their amplitudes?
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In general, the intensity of a wave is proportional to the square of its amplitude. This has an important implication: relative intensity can be obtained by squaring relative amplitude.
I α a2∴ a1 = √ I1 a2 I2 = √ 25 = 5 9 3
i.e., a1: a2 = 5:3
So if the intensity ratio is 25:9, the amplitude ratio will be 5:3.Correct Option: D
In general, the intensity of a wave is proportional to the square of its amplitude. This has an important implication: relative intensity can be obtained by squaring relative amplitude.
I α a2∴ a1 = √ I1 a2 I2 = √ 25 = 5 9 3
i.e., a1: a2 = 5:3
So if the intensity ratio is 25:9, the amplitude ratio will be 5:3.
- A bullet of mass ‘m’ and velocity ‘a’ is fired in to a large block of wood of mass ‘M’. The final velocity of the system is
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If v is the final velocity, then according to the principle of conservation of momentum,
m1v1 + m2v2 = (m1+m2)v;
or, v = m1v1 + m2v2/(m1+m2)
Using values from the question, v = m a + 0/ (m + M) = ma/ (m + M)Correct Option: B
If v is the final velocity, then according to the principle of conservation of momentum,
m1v1 + m2v2 = (m1+m2)v;
or, v = m1v1 + m2v2/(m1+m2)
Using values from the question, v = m a + 0/ (m + M) = ma/ (m + M)
- Which of the following property of sound is affected by change in air temperature
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The wavelength of sound changes with temperature. This is because the speed of sound changes with the temperature. Since the speed of sound is different at different temperature, this means the wavelength of sound at a given frequency is a variable depending on the speed of sound. For example, the wavelength of a 100 cycle tone in air at 68ºF would be 11.27 feet while the same tone in fresh water at 68ºF would have a wavelength of 48.05 feet.
Correct Option: D
The wavelength of sound changes with temperature. This is because the speed of sound changes with the temperature. Since the speed of sound is different at different temperature, this means the wavelength of sound at a given frequency is a variable depending on the speed of sound. For example, the wavelength of a 100 cycle tone in air at 68ºF would be 11.27 feet while the same tone in fresh water at 68ºF would have a wavelength of 48.05 feet.
- When water freezes its density
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Water at ordinary temperatures contracts and increases in density as it is cooled, like most substances. But at about 4°C it reaches a maximum density and then decreases in density as it approaches the freezing point. This is referred to as anomalous property of water.
Correct Option: A
Water at ordinary temperatures contracts and increases in density as it is cooled, like most substances. But at about 4°C it reaches a maximum density and then decreases in density as it approaches the freezing point. This is referred to as anomalous property of water.
- Which one of the following is a non-dimensional quantity?
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A dimensionless quantity is simply a quantity that has no units and therefore no dimensions. A ratio between two numbers is a non-dimensional or dimensionless quantity. Strain which is defined as change in dimension over original dimension has no dimensional formula. So it is a dimensionless quantity.
Correct Option: B
A dimensionless quantity is simply a quantity that has no units and therefore no dimensions. A ratio between two numbers is a non-dimensional or dimensionless quantity. Strain which is defined as change in dimension over original dimension has no dimensional formula. So it is a dimensionless quantity.
