Physik Aufgabe?Dringende Hilfe?

Hallo zusammen !

also ich hab hier auch eine Aufgabe, die ich für heute lösen muss und ich wollte nachfragen ob irgendjemand von euch meine Aufgabe also meine Lösung nachschauen könnte. Und falls da irgendein Fehler ist oder irgendetwas fehlt oder etwas besser gemacht werden muss, dann könnt ihr mir gerne helfen oder Bescheid sagen.

Hier ist meine Lösung:

a) Since only electrostatic forces act on the system, mechanical energy is conserved:

E initial=E final

The total energy consists of kinetic and electrostatic potential energy:

U_i + K_i = U_f + K_f

Since the spheres start from rest, the initial kinetic energy is zero:

U_i = U_f + K_f

Using Coulomb’s Law for electrostatic potential energy:

we write the energy conservation equation as:

where:

• r_i is the initial separation,

• r_f is the final separation,

• v_1 and v_2 are the velocities of q_1 and q_2,

• m_1 and m_2 are their respective masses

Since no external forces act on the system, linear momentum is also conserved:

m_1 v_1 = m_2 v_2

which gives:

v_1 = m2 *v2/m1

Substituting this into the energy equation:

Now we solve for v2:

and we get thqt it equals to 2.35 m/s

b)

Here we get that r minimum equals to 1m

Answer 1

[Clemens1973]

I think the exercise is meant somewhat differently, in a simpler way. The charge q1 is probably fixed here, and only q2 is movable.

a) For the potential energy of charge q1 in the field of charge q2, we have, as you wrote,

$E_\mathrm{pot}=\frac{q_1q_2}{4\pi\varepsilon_0r}$

The velocity at r_f=0.4m is given by

$\frac{q_1q_2}{4\pi\varepsilon_0r_\mathrm{i}}+\frac{1}{2}mv_\mathrm{2,i}^2=\frac{q_1q_2}{4\pi\varepsilon_0r_\mathrm{f}}+\frac{1}{2}mv_\mathrm{2,f}^2$

b) At the minimum distance r_min v_2 equals zero, so we have

$\frac{q_1q_2}{4\pi\varepsilon_0r_\mathrm{i}}+\frac{1}{2}mv_\mathrm{2i}^2=\frac{q_1q_2}{4\pi\varepsilon_0r_\mathrm{min}}$

(m=mass of sphere with charge q2).

Woher ich das weiß: Studium / Ausbildung

Comments

[JustAStudentBA]

Okay, so it means that the momentum of conservation is negligible?

[Clemens1973]

@JustAStudentBA

Yes, the momentum of charge q2 is absorbed by the support of charge q1/the Earth. That's how I understand the exercise...

[JustAStudentBA]

@Clemens1973

Thank you very much ! I really appreciate your help!