Answer:
Doppler shift of the starlight
Explanation:
To predict the movement of a star, we compare the spectra of elements found in star (H, He Na etc.), first spectra which are obtained from star and second spectra from laboratory. If spectral lines of the spectra obtained from star, are shifting towards red end (called red shift) then star is going away from earth and if shifting is towards blue (called blue shift), then star is approaching the earth. This is Doppler's shift.
A
most common source of phosphates in the soil is the weathering of the mineral apatite.
Explanation:
Apatite is a group of phosphate minerals like hydroxylapatite, fluorapatite, and chlorapatite. When apatite rocks weather, they release the phosphate minerals mainly in the form of PO₄ ³⁻ . These minerals become dissolved in water (hydrosphere), where they are readily available to plants and other organisms in the biosphere. The phosphates are taken up and used in biosynthesis. When these organisms die and become buried with sediments, the phosphate gets back to the lithosphere as sedimentary rock.
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For more on phosphorus cycle check out;
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Answer:False
Explanation:
Work is being done on a body when it causes displacement of body on the application of force
When we pull the door by a force it causes zero displacements of the door. So we can say that work done on it is zero.
Thus the above-given statement is false
Answer:
a. 5 × 10¹⁹ protons b. 2.05 × 10⁷ °C
Explanation:
Here is the complete question
A beam of protons is moving toward a target in a particle accelerator. This beam constitutes a current whose value is 0.42 A. (a) How many protons strike the target in 19 seconds? (b) Each proton has a kinetic energy of 6.0 x 10-12 J. Suppose the target is a 17-gram block of metal whose specific heat capacity is 860 J/(kg Co), and all the kinetic energy of the protons goes into heating it up. What is the change in temperature of the block at the end of 19 s?
Solution
a.
i = Q/t = ne/t
n = it/e where i = current = 0.42 A, n = number of protons, e = proton charge = 1.602 × 10⁻¹⁹ C and t = time = 19 s
So n = 0.42 A × 19 s/1.602 × 10⁻¹⁹ C
= 4.98 × 10¹⁹ protons
≅ 5 × 10¹⁹ protons
b
The total kinetic energy of the protons = heat change of target
total kinetic energy of the protons = n × kinetic energy per proton
= 5 × 10¹⁹ protons × 6.0 × 10⁻¹² J per proton
= 30 × 10⁷ J
heat change of target = Q = mcΔT ⇒ ΔT = Q/mc where m = mass of block = 17 g = 0.017 kg and c = specific heat capacity = 860 J/(kg °C)
ΔT = Q/mc = 30 × 10⁷ J/0.017 kg × 860 J/(kg °C)
= 30 × 10⁷/14.62
= 2.05 × 10⁷ °C
