# projectile q (1 Viewer)

#### GaganDeep

##### fffff
can any one explain this using 3u approach lo.

#### alcalder

No real need to use the 3 Unit maths approach. You would only use 3 unit integration if they were going to ask you to do things like:

- find the distance the electron travelled,
- find the time it took for the electron to leave the electric field and so on.

a) The energy gained from the acceleration in the electron gun is transformed into Kinetic Energy.

E = qV
E = 1.6 x 10-19 x 1000
= 1.6 x 10-16 J = ½ mv2
Thus v = √ (2 x 1.6 x 10-16/9.1 x -31)
v = 1.87 x 107m/s

b) Now, the electron enters the Electric field of strength 10000 N/C.
The horizontal veolcity has no effect on this calculation. It would be like throwing a ball off a cliff with a certain velocity. The acceleration due to gravity still acts in a verticle direction unaffected by the horizontal motion.

F = ma = Eq
9.1 x -31 a = 10000 x 1.6 x 10-19
Thus
a = 1.76 x 1015

#### Naylyn

##### Member
It takes a lot longer using the integration method:
E=V/d
E=1000/d

also
F=qE
F=1000q/d

now since F=ma
ma=1000q/d
a=1000q/md
d(v^2/2)/dx = 1000q/md
v^2/2 = 1000qx/md + C
v^2 = 2000qx/md + C
now at x=0 v=0
0=0 + C
v^2 = 2000qx/md

now for the required velocity x=d
v^2 = 2000q/m

not really worth effort is it...

#### sinist4

##### Member
dam.. for some reason that picture in the link is very small...

#### The Gate Keeper

##### Member
sinist4... click the picture!

It gives you a nice BIG version of it.

#### sinist4

##### Member
for some reason its still the same lol..ahh dw bout it
thanx dude anyway

#### Naylyn

##### Member
Where does E=qV come from?

#### helper

##### Active Member
Naylyn said:
Where does E=qV come from?
W=qV would have been better, so not confuse with E for electric Field strength

W=Fd
F=Eq
E=V/d

F=Vq/d
W=Vqd/d
W=qV

#### Naylyn

##### Member
ah thanks, the unfamiliar character confused me lol