(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

An electron is projected at an angle of 30.8° above the horizontal at a speed of 8.20×105 m/s in a region where the electric field is E = 388j N/C. Neglecting the effects of gravity, calculate the time it takes the electron to return to its initial height.

Answer: 1.23e-08 s

2. Relevant equations

v = v_0+at

F = qE = MA

3. The attempt at a solution

Components of Velocity

V_x = Vcos30.8

V_y = Vsin30.8

F = qE = ma

a = qE/m

= 1.6e-19*388/9.11e-31

= 6.81e13

V = v_0+at (set V = 0 cuz max height)

0 = v_y+at

t = 6.17e-9

Now i was playing with nums and found that if i multiplied V_y by 2 then divided it by a that is the right answer, why?

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Electrical kinematics

**Physics Forums | Science Articles, Homework Help, Discussion**