Find the voltage needed to accelerate the electron from rest

[0coffeebean0]

Homework Statement

An electron moving with a speed v can behave as wave with wavelength 6.4 x 10^-15 m. Given that the mass of electron = 9.1 x 10^-31 kg and the charge of electron is 1.6 x 10^-19 C, find
(a) the speed of v of the electron, and
(b) the voltage needed to accelerate the electron from rest until it acquires the speed v.

Homework Equations

The Attempt at a Solution

(a) wavelength = h / mv
v = h/ (m x wavelength)
= 1.1384 X 10^11 m/s

How do I calculate (b)? Please help, thank you. Kindly correct me if (a) is wrong.

 

[Noctisdark]

You are dealing with non-relativistic electron, right ? In that case i don't see any mistake in (a)
(b) Energy = charge * voltage, can you translate that to kinetic energy and pull a speed out of there ?
[EDIT: In case i wasn't clear, the potential energy which is E = e*V translates to kinetic energyenergy but that fact, e*V = mv^2 /2]

 

[Ceva]

The electron gains kinetic energy when moving at the speed you found. Think of the conservation of energy and from where it gained that energy.

 

[ehild]

Homework Statement

An electron moving with a speed v can behave as wave with wavelength 6.4 x 10^-15 m. Given that the mass of electron = 9.1 x 10^-31 kg and the charge of electron is 1.6 x 10^-19 C, find
(a) the speed of v of the electron, and
(b) the voltage needed to accelerate the electron from rest until it acquires the speed v.

Homework Equations

The Attempt at a Solution

(a) wavelength = h / mv
v = h/ (m x wavelength)
= 1.1384 X 10^11 m/s

How do I calculate (b)? Please help, thank you. Kindly correct me if (a) is wrong.

What is the speed of light? Can you use the rest mass of electron to calculate the momentum? See:
http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/relmom.html

 

[ehild]

You are dealing with non-relativistic electron, right ?

Can anything travel with 1.1384 X 10^11 m/s speed?

 

[Noctisdark]

Can anything travel with 1.1384 X 10^11 m/s speed?

Classically, Yes .

 

[ehild]

What is the speed of light?

Classically, Yes .

And in reality?

 

[Noctisdark]

What is the speed of light?

And in reality?

It doesn't, but people before the 19th thought that it was possible either way, you are extremely right, but as a homework he should use special relativity, i think, however sorry for that .