Accel. of eletron in Electric field.

[Lance WIlliam]

Homework Statement

How strong an electric field is needed to accelerate electrons in a TV tube from rest to one-tenth the speed of light in a distance of 5.5

Homework Equations

I used uniform accel. formula v^2=V_o_+2a(delta X)
v=3e7 (1/10th speed of light)
V_o_=Rest
m=9.11e-31(mass of eletron)
delta X= .055meters
all to find (a)
to find the Accelaration

and a=q/m(E)

The Attempt at a Solution

I need to find E i believe I came up with
a=2.72 m/s^2
and E= 3.98e-41 which was wrong...;/

Thankyou

 

[Doc Al]

I need to find E i believe I came up with
a=2.72 m/s^2

Redo that calculation. (Your equation is OK.)

 

[Lance WIlliam]

Ok I did it again and got 8.18e15 for my (a)
Then I need to find (E) so I changed the formula around so its "a/(q/m)=E" and I got 1.19e-33 ...wrong again...

 

[Doc Al]

Ok I did it again and got 8.18e15 for my (a)

Looks good.

Then I need to find (E) so I changed the formula around so its "a/(q/m)=E" and I got 1.19e-33 ...wrong again...

That formula, though oddly written (get that fraction out of the denominator), is perfectly OK. Redo the calculation.