com www.GOALias.blogspot.com www.GOALias ... - fun learning

www.GOALias.blogspot.comin Table 13.2. The first observationshown is just a sample. Yourobservations could be different fromthis. Repeat this activity a few times andrecord your observations. By dividingthe time taken for 20 oscillations by 20,get the time taken for one oscillation, orthe time period of the pendulum.Is the time period of your pendulumnearly the same in all cases?Note that a slight change in the initialdisplacement does not affect the timeperiod of your pendulum.Nowadays most clocks or watcheshave an electric circuit with one or moreTable 13.2 Time period of a simplependulumLength of the string = 100 cmS.No. Time taken for 20oscillations1. 42 s 2.1 s2.3.Time periodcells. These clocks are called quartzclocks. The time measured by quartzclocks is much more accurate than thatby the clocks available earlier.Units of time and speedThe basic unit of time is a second. Itssymbol is s. Larger units of time areminutes (min) and hours (h). Youalready know how these units are relatedto one another.What would be the basic unit ofspeed?Since the speed is distance/time, thebasic unit of speed is m/s. Of course, itcould also be expressed in other unitssuch as m/min or km/h.You must remember that thesymbols of all units are written insingular. For example, we write 50 kmand not 50 kms, or 8 cm and not 8 cms.Boojho is wondering how manyseconds there are in a day and howmany hours in a year. Can you helphim?There is an interesting story about the discovery that the time period of a givenpendulum is constant. You might have heard the name of famous scientistGalileo Galilie (A.D. 1564 –1642). It is said that once Galileo was sitting in achurch. He noticed that a lamp suspended from the ceiling with a chain wasmoving slowly from one side to the other. He was surprised to find that hispulse beat the same number of times during the interval in which the lampcompleted one oscillation. Galileo experimented with various pendulums toverify his observation. He found that a pendulum of a given length takes alwaysthe same time to complete one oscillation. This observation led to thedevelopment of pendulum clocks. Winding clocks and wristwatches wererefinements of the pendulum clocks.147MOTIONAND TIME147