The minute hand of a watch is 1.5 cm long. How far does its tip move in 40 minute?

in 40 minutes minute hand needle will rotate by an angle=360*40/60=240 degree=240*pi/180

                                                                                                                    =4pi/3 radian

so tip will move =r* theta

                       =1.5*4pi/3

                       =2pi c.m.