7. A particle of mass \( 2 k g \) is moving towards the origin along \( x \) with total kinetic energy \( 16 J \). It encounters a region where the potential energy \( u ( x ) \) is shown in the figure. Calculate its velocity when its distance \( x=4.5 m \) and the position of turning point.
a) \( (-9 m / s ) \vec{\imath}, 2.5 m \)
b) \( (-7 m / s ) \vec{i}, 3.1 m \)
c) \( (-3 m / s ) \vec{\imath}, 1.9 m \)
d) \( (-1.5 m / s ) \vec{i}, 1.2 m \)
