Recent content by Dana Fishel

Homework Statement An alpha particle (helium nucleus, charge +2e) starts from rest and travels a distance of 2.5 cm under the influence of a uniform electric field of magnitude 12.5 kV/m. What is the final kinetic energy of the alpha particle? Homework Equations U = 1/2 QV = 1/2 C(V^2) =...

Homework Statement In 1911, Ernest Rutherford discovered the nucleus of the atom by observing the scattering of helium nuclei from gold nuclei. If a helium nucleus with a mass of 6.68 10^-27 kg, a charge of +2e, and an initial velocity of 1.30 10^7 m/s is projected head-on toward a gold...

Never mind. I tried doing pheta = arcos of (-2/2.83) = -135degrees (since quadrant 3) and that's correct, but I don't really get why it works... Is it because the angle you get is the outside angle to the triangle? (Sorry this sounds really weird without the picture.) Thank you for your help...

I drew one, but can't get it to upload. So since both values are negative, it would be in quadrant 3, but I'm still confused about finding pheta. Since Ex and Ey make a triangle with the y and x-axis and we want to use tan, is pheta 90 degrees?

I wasn't sure about this so I tried +45 degrees and -45 degrees, but those are wrong. Would subtracting from 180 or 360 help?

Homework Statement Find the angle that makes with the positive x axis: (Consider vectors above the x-axis to make positive angles and vectors below the x-axis to make negative angles.) Homework Equations pheta = arctan (Ex/Ey) tan(pheta) = Ex/Ey The Attempt at a Solution I already found that...