Which of the following fields push on a stationary electron? (a) electric and gravitational fields but not magnetic fields. (b) gravitational fields but not electric or magnetic fields. (c) electric, magnetic, and gravitational fields. (d) magnetic and gravitational fields but not electric fields.

(A) electric and gravitational fields but not magnetic fields.

Explanation:

Let's analyze the effect produced by each of the three fields on the stationary electron:

- Gravitational force: the gravitational force exerted on the electron by a gravitational field is

where

m is the mass of the electron

g is the strength of the gravitational field

Since the mass of the electron m is non-zero, the electron experiences a gravitational force.

- Electric field: the electric force exerted on the electron by an electric field is

where

q is the charge of the electron

E is the magnitude of the electric field

Since the charge q of the electron is non-zero, the electron experiences an electric force.

- Magnetic field: the magnetic force exerted on the electron by a magnetic field is

where

q is the electron charge

v is the velocity of the electron

B is the magnitude of the magnetic field

is the angle between the direction of v and B

Since the electron is stationary, we notice that the velocity is zero: v=0, therefore the magnetic force is zero as well.

Therefore, the correct answer is

(A) electric and gravitational fields but not magnetic fields.

i had this question and the answer was 3.15 miles.

martina travels from school to her mom's office. from there, she walks to school. after school, she walks to the library and then to a friends house before finally ending back at home. find martina's total distance traveled.

a) 0 miles  

b) 0.4 miles  

c) 1 mile  

d) 3.15 miles

russian is not my first language, so i'm afraid i can't write out an answer in russian, but hopefully you can find a way to do so. here's my best translation of the problem: you're given a plot of a particle's position in one-dimensional space over time, and you're asked to find either the total distance traveled by the particle after 6 seconds had elapsed, or the total displacement of the particle after 6 seconds.

if you want the total distance traveled, you would first need to determine the particle's velocity as a function of time, then integrate that over the 6-second interval. we know the position function is quadratic with roots at 0 and 6, so we have

where is unknown. because the position is parabolic, there is symmetry about the midpoint at , and we know that

so that the position function is

which means the velocity is

then the total distance traveled is

so the total distance traveled is 20 m.

on the other hand, if you want to find displacement: the particle starts at and ends at , so its displacement is 0.