Electrical potential energy:
vf = v0/3
U0 = qV0
Uf = qVf
KE0 = (1/2)mv02
KEf = (1/2)mvf2 = (1/2)m(v0/3)2 = (1/18)mv02
A proton has an initial speed of 3.9 × 105 m/s.
What potential difference is required to reduce the initial speed of the proton by a factor of 3?