When an alpha particle is nearing the gold atoms nucleus, it is slowing down due to electrostatic repulsion, right? But then why is the acceleration or velocity not a minimum at that point (the point where the alpha particle reverses its direction)and why is the speed a minimum? Like isn't the resultant force on the alpha particle reducing which should cause its acceleration to be minimum?
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2 Answers
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The electrostatic repulsion force becomes larger as the particles are brought closer together. Since force is proportional to acceleration, this must mean that the acceleration is at a maximum when the particles are at their closest distance.
When something changes direction, the velocity vector changes direction. Therefore, at the point of changing directions the velocity is $0$.
answered Nov 25, 2018 at 15:54
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$\begingroup$ i know its kind of stupid, but wont resultant force be reduced as it nears the nucleus? $\endgroup$ Commented Nov 25, 2018 at 16:46
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$\begingroup$ @Meganmars The electrostatic force between two charges grows as they get closer. Can you explain your reasoning more? Maybe I am missing something. $\endgroup$ Commented Nov 25, 2018 at 19:09
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Isn't that because the electrostatic force invert the sense of the acceleration vector, reducing particle's speed to a minimum at that point? So the speed will be minimum, and acceleration maximum, but oriented in the opposite direction, which makes the alpha particle to reflect.
