GRADE SIX SCI­ENCE

Stabroek News Sunday - - WEEKEND MAGAZINE -

Happy New Year to you and your en­tire fam­ily! May you be suc­cess­ful in all that you do, es­pe­cially at your spe­cial as­sess­ment later in the year. Be sure to pay strict at­ten­tion in class and work as hard as you can. Re­vise a lot.

Have you made any New Year’s res­o­lu­tions? What are they? Share them with a friend or your par­ents.

How have you been keep­ing dur­ing the past few weeks that we did not have the Sci­ence ar­ti­cle? Have you been read­ing and re­vis­ing a lot? How did you spend Old Year’s night?

Did you en­joy find­ing out about levers last time? Have you been look­ing at levers all around you? Do re­mem­ber that good sci­en­tists are very ob­ser­vant. Where did you find the levers? Talk about this with your friends.

Last week we looked at the lever as a sim­ple ma­chine. This week we will look at the pul­ley. A pul­ley is a sim­ple ma­chine. It is re­ally a spe­cial kind of wheel with a grooved rim. A rope or chord fits into the groove. This pre­vents the rope or cord from slip­ping off. One end of the rope is at­tached to a load. When the rope is pulled, the pul­ley wheel turns and the load on the other end of the rope is moved.

You can make your own pul­ley. You will need a cot­ton reel, stiff wire or a wire clothes hanger, string and a load to lift. It is quite easy to make. Bend the wire (about 20cm) into a tri­an­gu­lar shape and push its ends into a cot­ton reel. Sus­pend (hang) this from a hook or bent nail. Next, tie one end of the rope, cord or string to a bucket or shoe or what­ever load you choose. (Look again at the pic­ture). Put the rope over the pul­ley. Now pull down on the string to raise the load.

You can make other pul­leys like those in the pic­ture be­low. Have you ever at­tended a flag-rais­ing cer­e­mony? Do you plan to at­tend this year’s Repub­lic flag rais­ing cer­e­mony, where one of the largest flags in the Caribbean will be hoisted? Have you ever looked care­fully at a flag pole and at how a flag is hoisted? Flag poles may be

found in front of many build­ings such as schools, min­istries and other of­fices. The per­son who raises the flag pulls down on the rope. As the rope is pulled down the flag goes up. The pul­ley makes it pos­si­ble to raise the flag in this way. Think care­fully and ex­plain how the flag is low­ered us­ing the pul­ley.

Pul­leys are not only found on the flag poles. Can you think of any places where pul­leys are found? They are found on the rafts above some gar­den wells, in el­e­va­tors and in ma­chines in fac­to­ries. Do you have any on the poles that sup­port your clothes lines?

There are dif­fer­ent kinds of pul­leys to be found. The main kinds are those that are fixed and those that are mov­able.A fixed pul­ley is at­tached to a wall or post or some other sup­port. It does not move, but ‘is fixed’ in place just as the pul­ley on the flag pole or clothes line is. A Fixed Pul­ley

A mov­able pul­ley is at­tached to the load. It moves as the load moves.

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