Consider the mass and a frictionless ramp shown in the ?gure. The mass is pushed upward with some initial velocity. Because of the in?uence of gravity it moves upward and reaches the highest point. It then turns around and moves downward. Starting from point A, along the way it passes consecutively the points B, C, D and E at equal time intervals. Denote by ?~vif the change in velocities between any pair of points (referred to as the initial and the ?nal points); i.e., ~vf = ~vi + ?~vif , where ~vi and ~vf are the corresponding velocity vectors at the two points. The direction of ?~vCD, i.e., the change of velocity vectors from C to D is
1. 0.
2. Uphill along the ramp if vA > 0.098 m/s, and downhill if vA < 0.098 m/s.
3. Uphill along the ramp if vA < 0.098 m/s, and downhill if vA > 0.098 m/s.
4. Uphill along the ramp.
5. Downhill along the ramp.