Let's see why g is 0 at centre of earth

Means g is indirectly proportional to height of object.
- If height is more gravity is less
- If height is less gravity is more
At centre h=0
- So if height is 0 then gravity is also zero.
And at centre the distance from top of earth surface is equal in opposite directions from centre.
So

Answer:
the magnetic field experienced by the electron is 0.0511 T
Explanation:
Given the data in the question;
Wavelength λ = 21 cm = 0.21 m
we know that Bohr magneton μ
is 9.27 × 10⁻²⁴ J/T
Plank's constant h is 6.626 × 10⁻³⁴ J.s
speed of light c = 3 × 10⁸ m/s
protein spin causes magnetic field in hydrogen atom.
so
Initial potential energy = -μ
B × cos0°
= -μ
B × 1
= -μ
B
Final potential energy = -μ
B × cos180°
= -μ
B × -1
= μ
B
so change in energy will be;
ΔE = μ
B - ( -μ
B )
ΔE = 2μ
B
now, difference in energy levels will be;
ΔE = hc/λ
2μ
B = hc/λ
2μ
Bλ = hc
B = hc / 2μ
λ
so we substitute
B = [(6.626 × 10⁻³⁴) × (3 × 10⁸)] / [2(9.27 × 10⁻²⁴) × 0.21 ]
B = [ 1.9878 × 10⁻²⁵ ] / [ 3.8934 × 10⁻²⁴ ]
B = 510556326.09
B = 0.0511 T
Therefore, the magnetic field experienced by the electron is 0.0511 T
<u>Answer</u>: The mass of the object is 25kg.
The given question deals with Newton's second law of motion and its applications.
<u>Explanation:</u> Given force, F=500N
acceleration, a=20 m/
From Newton's 2nd law of motion , we have
F=ma where m=mass of the object
⇒500=m×20
⇒m=500/20=25
∴ Mass of the object is 25 kg .
<u> </u><u>Reference Link: </u>brainly.com/question/1141170
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C.) a magnetic field is the correct answer…