An electron traveling horizontally to the right enters a region where a uniform electric field is directed downward. what is the direction of the electric force exerted on the electron once it has entered the electric field?

Upward

Explanation:

For charged particles immersed in an electric field:

- if the particle is positively charged, the direction of the force is the same as the direction of the electric field

- if the particle is negatively charged, the direction of the force is opposite to the direction of the electric field

In this problem, we have an electron - so a negatively charged particle - so the direction of the force is opposite to that of the electric field.

Since the electric field is directed downward, therefore, the electric force on the electron will be upward.

no. dot product   =0 when vecs at right angles