GRADE SIX SCIENCE
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.