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seguro https://session.masteringphysics.com/myct/itemView?assignmentProblemID=90798697&offset-next; ! EXAM 1 Item 11 c) 11 of 16 Constants 1 Periodic Table Part A An electron is at rest just above the surface of a sphere with a radius of 4.2 mm and a uniformly distributed positive charge of 1.9 10-15 C. Like a rocket blasting off from the Earth, the electron is given an initial speed ve radially outward from the sphere If the electron coasts to infinity, where its kinetic energy drops to zero what is the escape speed, ve? Express your answer using two significant figures. m/s Submit st Provide Feedback Next > e to searchExplanation / Answer
A)
q = charge on the electron = - 1.6 x 10-19 C
Q = charge on sphere = 1.9 x 10-15 C
r = radius of sphere = 4.2 mm = 0.0042 m
m = mass of electron = 9.1 x 10-31 kg
using conservation of energy
kinetic energy at the surface + electric potential energy at the surface = 0
(0.5) m ve2 - (k q Q/r) = 0
(0.5) (9.1 x 10-31) ve2 - (9 x 109) (- 1.6 x 10-19) (1.9 x 10-15)/(0.0042)
ve = 3.8 x 104 m/s
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