Answer:
Explanation:
The sum of the kinetic and electric potential energies of the proton when initially released must be equal to their sum at infinity, so we have:
Which, since 
because initially the proton is at rest, is:
where 
is Coulomb's constant, 
the charge of the proton, 
the charge of the gold nucleus, since it has 79 protons, 
the initial separation between them, 
the mass of the proton and v its final velocity. 
is very far away, so the final electric potential will be 0J, and we have:
0 to 30 takes more energy
Answer:
The angular speed of the system increases.
The moment of inertia of the system decreases.
Explanation:
As we know that the girl is going towards the center of the circle so here the moment of inertia of the girl is given as
here we know that
r = position of the girl from the center of the disc
now we know that the girl is moving towards the center so its distance will continuously decreasing
So the moment of inertia of the girl will decrease
Now we know that that with respect to the center of the disc there is no torque on the disc + girl system
So here we can use angular momentum conservation
So we have
since moment of inertia is decreasing for the system
so angular speed will increase
