A helium nucleus (charge +2e, mass  6.63 E-27 kg)
traveling at a speed of 6.2E5 m/s enters an electric
field, traveling from point A, at a potential of 1.5E3 V, to point B, at 4.00E3 V. What is its speed
at point B?

So, i started with ▲V=-▲KE/q
So, 2.5 = -▲KE/(3.2E-19)
So, ▲KE= -8E-19
From there i went to ▲=.5M(Vf^2-6.2E5^2)
I keep getting 6.19E5 for my final velocity whereas the correct answer is 3.78E5. I know im in the right direction since it is supposed to be slowing down.
Thanks for any and all help!

Question

A helium nucleus (charge +2e, mass  6.63 E-27 kg)
traveling at a speed of 6.2E5 m/s enters an electric
field, traveling from point A, at a potential of 1.5E3 V, to point B, at 4.00E3 V. What is its speed
at point B?

So, i started with ▲V=-▲KE/q 
So, 2.5 = -▲KE/(3.2E-19)
So, ▲KE= -8E-19
From there i went to ▲=.5M(Vf^2-6.2E5^2)
I keep getting 6.19E5 for my final velocity whereas the correct answer is 3.78E5. I know im in the right direction since it is supposed to be slowing down.
Thanks for any and all help!

anonymous · Answer

you can use the conservation of energy. while alpha particle moves along the electric field, it loses 5 KeV. 
then you should find the initial kinetic energy of alpha particle in terms of KeV. Then use conservation of energy you will get final kinetic energy of alpha particle.. after that you can calculate final velocity of alpha particle by using  (mv^2)/2 = Kinetic energy

anonymous · Answer

what do you mean by "alpha particle"?

anonymous · Answer

Helium nucleus is same thing with the alpha particle.