A circuit consists of a rigid U-shaped conductor of negligible resistance and a bar that is able to slide along the U-shaped conductor without mechanical resistance. The length of bar between the contacts is ܽ ൌ15cm. The bar has a mass ݉ൌ0.25kg and a resistance ܴ ൌ8.0Ωbetween the contacts. The power supply produces a potential difference of 2800V. The entire apparatus is in a region of uniform magnetic field ܤ ൌ1.5T. The circuit is completed at time ݐൌ0s. Express the position of the bar as a function of time for the time that the bar is in contact with the U-shaped conductor.