After exactly 12:00, the minute and hour hands first become perpendicular after N/11 minutes. Find N.

Question

G1 Physics · Accepted Answer

At 12:00 both hands coincide. Their relative angular speed is 6−0.5=5.5°/min = 11/2°/min. The first perpendicular configuration requires a relative angular separation of 90°. Therefore t=90/(11/2)=180/11 min. Hence N=180.