Vector evaluation & Lorentz force 02

[Roodles01]

Homework Statement

An electron in electric & magnetic fields;
E = 3.0x10⁷ e_x NC-1
B = 3.0 e_z T
has velocity
v = 1.0x10^7 (2e_x-e_y)

Calculate em force on the electron.

Homework Equations

I'm using the Lorentz force law here.
F = q(E + v X B)

I have an example solution using vectors to evaluate direction

| e_x_______e_y_______e_z |
| 2.0x10⁷_ 1.0x10⁷ __ 0 |
| 0_______0________3.0 |

The Attempt at a Solution

I think this has been posted as the solution to vXB,but then why is the E value 3.0 T there?

Could someone please ecplain why this is.

 

[TSny]

I have an example solution using vectors to evaluate direction

| e_x_______e_y_______e_z |
| 2.0x10⁷_ 1.0x10⁷ __ 0 |
| 0_______0________3.0 |

The Attempt at a Solution

I think this has been posted as the solution to vXB,but then why is the E value 3.0 T there?

Could someone please ecplain why this is.

3.0 T is the B value, not the E value.

 

[Roodles01]

Oops, a typo, yes, but why is it there, how does it relate to the Lorentz law & is the solution

Final calculation 9.6x10^-12 N

I seem to not be able to attach workings in a picture file, sorry.

 

[TSny]

The determinant will give you the cross product of v and B. The result of the determinant will be a vector. You then need to add the vector E to v x B and finally multiply by q.

 

[Roodles01]

OK
vXB = e_x (3.0x10⁷ - 0) + e_y (-6.0x10⁷ - 0) + e_z (0)

q(vXB)= -e (3.0x10⁷ e_x + (-3.0x10⁷ e_x - 6.0x10⁷ e_y) + 6.0x10⁷ * 1.6x10^-19 e_y) N

F = 9.6x10^-12 e_y N