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WAEC Physics 2019 Paper

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Question : 30

Total: 49

An electron of mass 9.1 x 10

^{-31}

kg moves with a speed of 2.0 x 10

^6

^{-1}

round the nucleus of an atom in a Circular path of radius 6.1 x 10(^{11}\) m. Determine the angular speed of the electron.

3.28 x 10 $^{16}$ rad s $^{-1}$
8.55 x 10 $^{3}$ rad s $^{-1}$
9.11 x 10 $^{13}$ rad s $^{-1}$
5.22 x 10 $^{15}$ rad s $^{-1}$

Solution:

Angular speed of the electron (W)

w = $\;\frac{\text{Velocity}}{\text{Radius}} = \;\frac{V}{R}$

= $\;\frac{2.0 \; \times \; 10^6}{6.1 \; \times \; 10^{11}}$

= 3.28 x 10 $^{16}$ rads $^{-1}$

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