A person travelling in a straight line moves with a constant velocity \(v_1\) for a certain distance \(x\) and with a constant velocity \(v_2\) for the next equal distance. The average velocity \(v\) is given by the relation:
1. | \(\frac{1}{v} = \frac{1}{v_1}+\frac{1}{v_2}\) | 2. | \(\frac{2}{v} = \frac{1}{v_1}+\frac{1}{v_2}\) |
3. | \(\frac{v}{2} = \frac{v_1+v_2}{2}\) | 4. | \(v = \sqrt{v_1v_2}\) |