A body of mass 1 kg is rotating in a vertical circle of radius 1 m. What will be the difference in its kinetic energy at the top and bottom of the circle in joules? Take g = 10 m s⁻².
Physics · Mixed Chapter
JEE Main Practice

Question

A body of mass 1 kg is rotating in a vertical circle of radius 1 m. What will be the difference in its kinetic energy at the top and bottom of the circle in joules? Take g = 10 m s⁻².

G1 Physics · Accepted Answer

Step 1: Height difference between lowest and highest positions = 2r = 2 m. Step 2: Tension in the string is perpendicular to instantaneous displacement and does no work. Step 3: By conservation of mechanical energy, Kbottom − Ktop = mg(2r). Step 4: Difference = 1 × 10 × 2 = 20 J. Final answer: 20 J.