A thin uniform straight rod of mass 2 kg and length 1 m is free to rotate about its upper end when at rest. It receives an impulsive blow of 10 Ns at its lowest point, normal to its length as shown in figure. Find the kinetic energy of rod just after impact.

Question

G1 Physics · Accepted Answer

Angular impulse about the pivot is JL=Iₐω. For a uniform rod Iₐ=(1/3)ML²=(1/3)(2)(1²)=2/3 kg·m². Thus ω=(10×1)/(2/3)=15 rad/s. K=½Iω²=½(2/3)(225)=75 J.