The area of cross-section of a railway track is 0.01 m². The temperature variation is 10$$^\circ$$C. Coefficient of liner expansion of material of track is 10^$$-$$5/$$^\circ$$C. The energy stored per meter in the track is ____________ J/m.

(Young's modulus of material of track is 10¹¹ Nm^$$-$$2)

The centre of a wheel rolling on a plane surface moves with a speed v₀. A particle on the rim of the wheel at the same level as the centre will be moving at a speed $$\sqrt x {v_0}$$. Then the value of x is _____________.