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Q.(a) Give an example for a body possessing zero velocity which is accelerating.
(b) Show that area under velocity-time graph gives displacement.
Kerala DhseKerala DHSE Plus One Board 2023Subjective· 3mImportance★★★★★
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Start your 14-day free trial to unlock the full solution →A body can have zero velocity and non-zero acceleration simultaneously (e.g., a ball at the top of its vertical flight); and the area enclosed between a velocity–time graph and the time axis represents the displacement, because each thin vertical strip v·dt of that area is itself a small displacement.
- Consider a ball thrown vertically upward. As it rises, gravity continuously decelerates it. At the highest point of its path, its velocity becomes exactly zero for an instant — but gravity has not stopped acting on it; the ball still has acceleration a = g, directed downward, at that very instant (which is why it immediately starts to fall back down). This is a clear example of a body having zero velocity while still being accelerated. (Another valid example: a simple pendulum at its extreme position — velocity is zero there, but the restoring acceleration is maximum.)
- Consider a body moving with velocity v(t), and take a very small time interval dt around some instant t, during which the velocity may be taken as approximately constant. The small displacement in this interval is dx = v dt On a velocity–time graph, v is plotted on the vertical axis and t on the horizontal axis. The quantity v·dt is exactly the area of a thin vertical strip of width dt and height v under the graph at that instant. The total displacement between times t1 and t2 is the sum (integral) of all such small displacements: x = ∫ v dt (from t1 to t2) …
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