Two stationary positive point charges, charge 1 of magnitude 3.15 and charge 2 o

Question

Two stationary positive point charges, charge 1 of magnitude 3.15 and charge 2 of magnitude 2.00 , are separated by a distance of 48.0 . An electron is released from rest at the point midway between the two charges, and it moves along the line connecting the two charges.
What is the speed of the electron when it is 10.0 from charge 1?
vfinal= _______________m/s

then...
Two stationary positive point charges, charge 1 of magnitude 4.00 and charge 2 of magnitude 1.65 , are separated by a distance of 38.0 . An electron is released from rest at the point midway between the two charges, and it moves along the line connecting the two charges.
What is the speed of the electron when it is 10.0 from charge 1?
vfinal=______________ m/s

Explanation / Answer

applying conservation of energy initial PE = PE with 3.15charge + PE with2.00 charge =                  = k Q q / r       + k Q q/ r   =     = 8.99 x 109 * 3.15 x 10-9 * -1.60 x10-19 / 0.24 +   8.99 x109 * 2.0 x 10-9 * -1.60 x 10-19/ 0.24       =   - 308.65 x 10-19 Joules    final PE      = k Q q / r       + k Q q/ r   =    = 8.99 x 109 * 3.15 x 10-9 * -1.60 x10-19 / 0.10 +   8.99 x109 * 2.0 x 10-9 * -1.60 x 10-19/ 0.38     =   - 528.80 x 10-19 Joules      change in PE = finalPE - initial PE = -528.80  - (-308.65 ) =    -220.15 x10-19 Joules     The increase in kinetic energy must equalthe decrease in PE, so final KE = 220.15 x10-19 Joules and     K = (1/2) mv2          v = ( 2 K / m )1/2 =                                        = ( 2 * 220.15 x 10-19 / 9.11 x 10-31)1/2                                       = 6.9521 * 106 m/s    please post second post next time. I will do that thank U    = 8.99 x 109 * 3.15 x 10-9 * -1.60 x10-19 / 0.10 +   8.99 x109 * 2.0 x 10-9 * -1.60 x 10-19/ 0.38     =   - 528.80 x 10-19 Joules      change in PE = finalPE - initial PE = -528.80  - (-308.65 ) =    -220.15 x10-19 Joules     The increase in kinetic energy must equalthe decrease in PE, so final KE = 220.15 x10-19 Joules and     K = (1/2) mv2          v = ( 2 K / m )1/2 =                                        = ( 2 * 220.15 x 10-19 / 9.11 x 10-31)1/2                                       = 6.9521 * 106 m/s    please post second post next time. I will do that thank U                                       = 6.9521 * 106 m/s    please post second post next time. I will do that thank U

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