In this question, you may assume that non-relativistic calculations are adequate

Question

In this question, you may assume that non-relativistic calculations are adequate. Given your answers to at least three significant figures. Answers must be accurate to 1%. An electron has a wavelength of 5.6 times 10^-9 m. What is the momentum of the electron? 2.137756 times 10^-26 2.843215 times 10^-26 3.781476 times 10^-26 5.029363 times 10^-26 6.689053 times 10^-26 8.896441 times 10^-26 1.183227 times 10^-25 1.573691 times 10^-25 kg m/s What is the speed of the electron? __________ m/s What is the kinetic energy of the electron? ________ J

Explanation / Answer

wavelength of electron = 5.6 x 10^ -9 m

we have formula wavelength lamda = h / p    where h is plankc ocnstant , P is momentum

              5.6 x 10^ -9 m = ( 6.625x10^-34 m/s) / ( p)

   p = 1.183 x 10^ -25

2) we have fomula momentum p = m x v  

where m = mas of electron = 9.1 x 10^ -31 kg

now 1.183 x 10^ -25   = 9.1 x 10^ -31 kg x v          where v is speed of electron

v = 1.3 x 10^ 5 m/s

Kinetic energy of electron = 1/2 x m x v^2

                  = ( 1/2) x 9.1 x 10^ -31 kg x ( 1.3x10^5 m/s)^2

                = 7.7 x 10^ -21   kgm^2 /s2

           = 7.7 x 10^ -21 J         ( since J = kgm2/s2)

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