choose 2 correct option about motion in a straight line.
1. if a vechile has a zero velocity it must be stationary 2.the graph of position against time has to be a st.line 3.acceleration is the rate of change of speed 4.velocity is the rate of change of position 5.a reversing vechile must have negative velocity 6.two vechiles travelling at the same speed at the same instant of time on the same road must have the same velocity.