Couldn't you merely relative the kinetic energy to its velocity, and hence the velocity to its radius? When you know the radius of the path taken, then you can determine where its position is when its travels half the circumfrence of a circle.
This is the question I am having difficult with. I really have no idea where to start.
Here's what I have gathered with the information provided:
Using the right hand rule, I've concluded v points along the x axis, the the force acting on the particle point along the z axis. Since the electron is under the influence of the magnetic field, and its radial acceleration is opposite in direction to the force, it will follow the path of a circle in the negative z direction. From here, I don't know where to go..
Thanks in advance.
The velocity is initially in the x direction. As the electron enters the magnetic field, you have the correct direction for the force. However, the force in the negative z direction gives the electron a component of velocity in that direction. So the force will also begin to change direction. Since the force is always perpendicular to the velocity vector, the speed (magnitude of the velocity) will not change & the electron will begin to undergo uniform circular motion.