Practice Problem 18. Constants acceleration is not constant Now let\'s look at t

Question

Practice Problem 18. Constants acceleration is not constant Now let's look at the potential enegy of a charge that is in the vicinity of two other charges Suppose two electrons are held in place 10 0 cm apart Ploint a s midway between he two electrons, and point b is 120 em directy above point a (a) Calculate the electric potental at point a and atl point & (b) A trd electron is released from rest at point b What is the speed of th electron when it is far from the other two electrons? The mass of an electron is Note that the net force on the third electron decreases as that electron moves away trom point b Its so constant -acceleration equations cannot be used to find its fienal speed. But conservation of energy principles are easy to apply Part A-Practice Problem econ at port b.s replaced with a proton (mass m,=1.67x10," kg)that neleased honrest and accelerates oward point a What is the speed of the peoton when it reaches point a? Express your answer in meters per second to two significant figures Figure 1 of m/s 134 120 cm Submd 60 60 cm Next ) Provide Feedback

Explanation / Answer

Electric potential at point a,

Va = k q1 / r1 + k q2 / r2

= 2 (9 x 10^9 x - 1.6 x 10^-19 / (0.05))

= - 5.76 x 10^-8 Volt

Vb = 2(9 x 10^-9 x -1.6 x 10^-19)/0.13) = - 2.215 x 10^-8 Volt

for proton:

PEi + KEi = PEf + KEf

(1.6 x 10^-19)(- 2.215 x 10^-8) + 0 = (1.6 x 10^-19)(- 5.76 x 10^-8) + ( 1.67 x 10^-27)v^2 / 2

v = 2.61 m/s ..........Ans

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