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Physics Obj-
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21-30:

(5a)
Heat capacity of a body is the amount of heat energy required to change the temperature of the body by a given amount. It is measured in joules per kelvin (J/K).


(5b)
Q = mcΔT

where:
Q = heat energy (in joules, J)
m = mass of water (in kilograms, kg)
c = specific heat capacity of water (in J/kgK)
ΔT = temperature change (in kelvin, K)

Given values:
m = 100 g = 0.1 kg (converted to kilograms)
c = 4200 J/kgK
ΔT = 20°C = 20 K (since 1°C = 1 K)

Plugging in the values:

Q = 0.1 kg × 4200 J/kgK × 20 K
= 8400 J
= 8.4 kJ

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6)
(i) Atmospheric conditions: During the day, the atmosphere is more turbulent and chaotic, with warm air rising and cooler air sinking. This turbulence scatters sound waves, making them less focused and less intense. In contrast, the atmosphere at night is generally calmer and more stable, allowing sound waves to travel more directly and with less scattering. This reduced scattering enables sounds to reach our ears with greater clarity and intensity.

(ii) Temperature gradients: This also play a role in sound propagation. During the day, the ground and surrounding objects absorb and radiate heat, creating a temperature gradient that affects sound wave propagation. At night, the temperature gradient is reduced, allowing sound waves to travel more efficiently through the atmosphere.

(iii) Humidity: This is another factor that influences sound propagation. Daytime humidity can absorb and scatter sound waves, reducing their intensity. In contrast, nighttime air is often drier, allowing sound waves to travel farther without attenuation.

(iv) Background noise: This is a significant factor in our perception of sound. Daytime environments are often filled with background noise from human activity, traffic, and other sources. This background noise can mask subtle sounds, making them less noticeable. At night, this background noise is reduced, making sounds more prominent and audible.

(v) Psychological factors: This also contribute to our perception of sound at night. Our brains are more sensitive to sounds in quiet environments, making us more aware of subtle sounds that might be masked during the day. This increased sensitivity, combined with the reduced background noise, makes sounds seem more intense and clearer at night.

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Physics obj
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11-20:BABDCBACAD
21-30:EEAEBCEDCB
31-40:DDDCDADEBA
41-50:ADE

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Physics obj
1-10:CCABCABBBB
11-20:BABDCBACAD
21-30:EEAEBCEDCB
31-40:DDDCDADEBA
41-50:ADEBBCDAE
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