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Liquid_Explosion
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#1
Report Thread starter 14 years ago
#1
1. The intensity of the Sun's radiation is approximately 1370 W m^-2 at the distance of the Earth from the Sun (150 x 10^9m). Estimate the total power output from the Sun. (Surface area of sphere of radius r=4πr^2.)

2. An oscillator is used to send waves along a streched cord. The cord is 20cm long, and four complete waves fit along its length when the oscillator vibrates 30 times per second. For the waves on the string:

a) what is their wavelength?

b) what is their frequency?

c) what is their speed?
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lukeD
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#2
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Answer to q1:

Think of a huge sphere surrounding the sun, with its radius as the distance to the Earth.

The surface area of this sphere = 4π x (150^9)^2
= 2.83 x 10^23 m^2

We know that, at the distance of the Earth from the Sun, the intensity of radiation is 1370 W per square metre.

Therefore, total power output = 1370 x (2.83 x 10^23)
= 3.88 x 10^26 W
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elpaw
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#3
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2 a) 20/4 = 5 cm

b) 30 "times per second" = 30 Hz

c) v = f.lambda = 5 * 30 = 150 cm/s = 1.5 m/s
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london_bum
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#4
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Yay! I just tried doing them and I got the same answers as the people above me! At least I remember something.
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Liquid_Explosion
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#5
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yea i just wanted to check number 2 and it seems i got it right. I didnt really understand number 1 nd was a bit confused.

Thanks 4 help ppl.
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