Avelocity selector consists of electric and magnetic fields described by the expressions e = e k and b = b ĵ, with b = 12.0 mt. find the value of e (in kv/m) such that a 770 ev electron moving in the negative x-direction is undeflected.

massxgravity x heght=weightxheight= pe

4900=490xh

h=10

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.