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There is a uniform spherically symmetric surface charge density at a distance R 0 from the origin. The charge distribution is initially at rest and starts expanding because of mutual repulsion. The figure that represents best the speed V (R(t)) of the distribution as a function of its instantaneous radius R (t) is :

1. R 0 R (t) V(R(t))
2. R 0 R (t) V 0 V(R(t))
3. R 0 R (t) V(R(t))
4. R 0 R (t) V(R(t))

Correct answer: R 0 R (t) V 0 V(R(t))

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