Rahul claims that because the speed of a stone tied to a string and whirled in a horizontal circle is constant, the velocity–time graph for this motion must be a straight horizontal line. Analyse Rahul’s claim by answering the parts below.
a. (i) Distinguish between speed and velocity for an object in circular motion.
b. (ii) Explain why a horizontal line cannot represent the velocity–time graph of uniform circular motion, even though the speed remains constant.
c. (iii) Without using any numerical values, sketch a qualitative velocity–time graph for one complete revolution, clearly indicating how it differs from a speed–time graph.
d. (iv) State what physical quantity changes continuously in this motion and why this leads to the presence of acceleration.