Velocity must be positive.

"Student difficulties in connecting graphs and physics: Examples from kinematics," L.C. McDermott, M.L. Rosenquist and E.H. van Zee, Am. J. Phys., 55, 503-513 (1987).

"Student difficulties with graphical representations of negative values of velocity," F. M. Goldberg and J. H. Anderson, Phys. Teach. 27, 254-260 (1989).

Same position means same speed.

"Investigation of student understanding of the concept of velocity in one dimension," D.E. Trowbridge and L. C. McDermott, Am. J. Phys. 48, 1020-1028 (1980).

Leading (following) particle moves at a faster (slower) speed.

"Investigation of student understanding of the concept of velocity in one dimension," D.E. Trowbridge and L. C. McDermott, Am. J. Phys. 48, 1020-1028 (1980).

Same velocity means same acceleration for two objects.

"Investigation of student understanding of the concept of acceleration in one dimension," D.E. Trowbridge and L. C. McDermott, Am. J. Phys. 49, 242-253 (1981).

Larger (smaller) velocity means larger (smaller) acceleration.

"Investigation of student understanding of the concept of acceleration in one dimension," D.E. Trowbridge and L. C. McDermott, Am. J. Phys. 49, 242-253 (1981).

Zero velocity means zero acceleration.

"Investigation of student understanding of the concept of acceleration in one dimension," D.E. Trowbridge and L. C. McDermott, Am. J. Phys. 49, 242-253 (1981).

A positive slope for a negative velocity means the object is speeding up.

"Student difficulties with graphical representations of negative values of velocity," F. M. Goldberg and J. H. Anderson, Phys. Teach. 27, 254-260 (1989).

Students plot position and velocity graphs as the path of the particle.

"Student difficulties in connecting graphs and physics: Examples from kinematics," L.C. McDermott, M.L. Rosenquist and E.H. van Zee, Am. J. Phys., 55, 503-513 (1987).

Velocity is intrinsic to a particle, and doesn't depend on the observer (i.e. the ground is a preferred observer).

"Student preconceptions about vector kinematics," J.M. Aguirre, Phys. Teach. 26, 212-216 (1988).

"Displacement, velocity and frames of reference: Phenomenographic studies of students' understanding and some implications for teaching and assessment," J. Bowden, G. Dall'Alba, E. Martin, D. Laurillard, F. Marton, G. Masters, P. Ramsden, A. Stephanou and E. Walsh, Am. J. Phys. 60, 262-269 (1992).