Answer on Question #43091-Physics-Atomic Physics
Estimate the orbital velocity in m/s of an electron orbiting the nucleus of a hydrogen atom at a radius of 0.05 nm.
SOLUTION:
The centripetal force which keeps the electron in orbit is provided by the electric force.
m v 2 r = k e 2 r 2 \frac {m v ^ {2}}{r} = \frac {k e ^ {2}}{r ^ {2}} r m v 2 = r 2 k e 2
So,
v = k m r e = 9 ⋅ 1 0 9 N m 2 C 2 9.11 ⋅ 1 0 − 31 k g ⋅ 0.05 ⋅ 1 0 − 9 m ⋅ 1.6 ⋅ 1 0 − 19 C = 1.4 ⋅ 1 0 6 m s . v = \sqrt {\frac {k}{m r}} e = \sqrt {\frac {9 \cdot 1 0 ^ {9} \frac {N m ^ {2}}{C ^ {2}}}{9 . 1 1 \cdot 1 0 ^ {- 3 1} k g \cdot 0 . 0 5 \cdot 1 0 ^ {- 9} m}} \cdot 1. 6 \cdot 1 0 ^ {- 1 9} C = 1. 4 \cdot 1 0 ^ {6} \frac {m}{s}. v = m r k e = 9.11 ⋅ 1 0 − 31 k g ⋅ 0.05 ⋅ 1 0 − 9 m 9 ⋅ 1 0 9 C 2 N m 2 ⋅ 1.6 ⋅ 1 0 − 19 C = 1.4 ⋅ 1 0 6 s m .
Answer: 1.4 ⋅ 1 0 6 m s 1.4 \cdot 10^{6} \frac{m}{s} 1.4 ⋅ 1 0 6 s m .
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