A proton is fired toward a lead nucleus from very far away. How much initial kinetic energy does the proton need to reach a turning point 10 fm from the nucleus?

The electric force is conservative.

Since

ΔK = −ΔU,

Kf − Ki =Ui −Uf.

We have,

Kf = 0

Ui = 0.

Thus Ki =Uf.

so ,at 10 fm Uf = (2×10)−12 J.

metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

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