Draw the $x-t$ graphs for positive,negative,and zero acceleration.

(N/A) The $x-t$ (position-time) graph represents the motion of an object. The slope of the $x-t$ graph gives the velocity of the object. The curvature of the graph indicates the acceleration.
$(a)$ For positive acceleration $(a > 0)$: The graph is concave upwards (like a parabola opening upwards). The velocity increases with time.
$(b)$ For negative acceleration $(a < 0)$: The graph is concave downwards (like a parabola opening downwards). The velocity decreases with time.
$(c)$ For zero acceleration $(a = 0)$: The graph is a straight line with a constant slope,indicating constant velocity.