# Math Help - kinetic energy

1. ## kinetic energy

Point A is at a potential of +240 V, and point B is at a potential of -120 V. An -particle is a helium nucleus that contains two protons and two neutrons;

the neutrons are electrically neutral. An -particle starts from rest at A and accelerates toward B.

When the -particle arrives at B, what kinetic energy (in electron volts) does it have?
in eV

2. Originally Posted by rcmango
Point A is at a potential of +240 V, and point B is at a potential of -120 V. An -particle is a helium nucleus that contains two protons and two neutrons;

the neutrons are electrically neutral. An -particle starts from rest at A and accelerates toward B.

When the -particle arrives at B, what kinetic energy (in electron volts) does it have?
in eV

$W = q \Delta V$

What's q? What's $\Delta V$? How does the work done on the alpha particle relate to its kinetic energy?

-Dan

3. q is the charge stored by a dialectric capacitor.

and change in V is the electric potential difference.

chng in V = Vb - Va = -360 V correct?

so where does the q come from?

4. the answer is in EV maybe q has somthing to do with the electron? dont quote i have been out of school for too long

5. Originally Posted by rcmango
q is the charge stored by a dialectric capacitor.

and change in V is the electric potential difference.

chng in V = Vb - Va = -360 V correct?

so where does the q come from?
No, the q is the charge on the alpha particle.

Yes, $\Delta V = -120~V - 240~V = -360~V$.

-Dan

6. Originally Posted by Destiny666
the answer is in EV maybe q has somthing to do with the electron? dont quote i have been out of school for too long
The unit "eV" stands for "electron Volts." It is a unit of energy related directly to the amount of kinetic energy gained by a positron being accelerated over an electric potential of 1 V. $1~eV = 1.6 \times 10^{-19}~J$.

-Dan

7. ## I am sure that is right

Ek=(Vb-Va)xq
= (-120-240)x2x1.602x〖10〗^(-19)
=-360x3.204x〖10〗^(-19)
≈-1153x〖10〗^(-19)V[/SIZE]

Ek is the kinetic energy
Va is the potential at A
Vb is the potential at B

8. Originally Posted by blertta
Ek=(Va-Vb)xq
= (240+120)x2x1.602x〖10〗^(-19)
=360x3.204x〖10〗^(-19)
≈1153x〖10〗^(-19)V[/SIZE]

Ek is the kinetic energy
Va is the potential at A
Vb is the potential at B
Except that they want the answer in eV. (By the way, your answer has the wrong unit! I think you meant "VC" which is equal to a J.)

-Dan