Reni has made a pendulum by tying a stone to a string. Its time period is 0.5s. Can you help Reni to redesign her pendulum with a time period of 1 second? (i) How will you help her to achieve this? (ii) State the factor on which the time period of a pendulum depends so that Reni can redesign her pendulum

Engines for propeller-driven aircraft are limited in their maximum rotational speed by the fact that the tip speed of the propeller must not approach the speed of sound in air (mach i). taking 6 ft as a typical diameter for a propeller of a light airplane and 1100 fils as the speed of sound, find the upper limit on the rpm (revolutions per minute) of the propeller shaft.