Physics · Motion In A Straight Line · NEET
Read the SLOPE of the v-t graph in each section, and that slope is the acceleration value you plot. If the v-t line goes up (positive slope), a is positive. If the v-t line is flat (zero slope), a = 0. If the v-t line goes down (negative slope), a is negative. So a straight v-t line always gives a flat (horizontal) a-t line, because its slope is one fixed number.
The area under the a-t graph gives the CHANGE in velocity, not the velocity itself. From a = delta v / t, we get delta v = a x t, which is exactly the area (height a times width t). To get the final velocity you must add this area to the starting velocity: v = u + area. This is the a-t version of the rule 'area under v-t = displacement.'
For constant velocity the acceleration is zero, so the a-t graph is a horizontal straight line lying exactly on the time axis (a = 0). Do not confuse this with the v-t graph, which for constant velocity is a horizontal line ABOVE the axis. Constant velocity means no acceleration, so the a-t graph sits at zero.
Uniform acceleration means a does not change with time, it is one fixed value. When you plot a fixed number against time you get a horizontal line parallel to the time axis. It is above the axis for positive a and below the axis for negative a (retardation). Only the v-t graph slants for uniform acceleration; the a-t graph stays flat.
Break the v-t graph into pieces and check the slope sign of each piece. Rising v-t part gives a positive step, flat v-t part gives a = 0 (on the axis), falling v-t part gives a negative step. Then find the a-t option that has the SAME sequence of positive, zero, and negative pieces. Match the pattern of signs, section by section.
The velocity (v)-time (t) graph of a body moving in a straight line first rises (v increases), then stays flat (v constant), then falls (v decreases). Which acceleration (a)-time (t) graph best represents this motion?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Acceleration is the slope of the velocity-time (v-t) graph. On the acceleration-time (a-t) graph, acceleration is simply the height of the line itself, and its slope has no standard name in NEET kinematics.
Area under a v-t graph gives displacement (how far the body moved). Area under an a-t graph gives the change in velocity, delta v = a x t. Both are 'area = the next quantity' rules, one level apart.
Yes. A negative acceleration (retardation or acceleration in the negative direction) plots below the time axis. Area below the axis counts as a negative change in velocity, meaning the velocity decreases.
Find the area under the a-t graph to get delta v, then use v = u + delta v, where u is the initial velocity. For a rectangle, area = a x t; for a triangle, area = (1/2) x base x height.
Uniform acceleration means the acceleration value never changes, so plotting one fixed number against time gives a horizontal straight line. It is a common NEET trap because students expect it to slant like the v-t graph.
