SECTION ONE: Comprehension.
Read the following dialogue then do the activities below.
Ball-bearing
Since man began to need to move things, he has used round rollers to make the job easier. Probably the first rollers were sticks or logs, which were a big improvement over dragging things across the ground, but still difficult work.In 1794, Welsh ironmaster Philip Vaughan invented a device which made the task of moving things much easier. It was the ball-bearing. Ball-bearings are mechanical devices to support the axle of a carriage. Development continued in the nineteenth and early twentieth centuries, encouraged by the advancement of the bicycle and the automobile.
There are thousands of sizes, shapes, and kinds of rolling bearings; ball-bearings, roller bearings, needle bearings, and tapered roller bearings are the major kinds. Sizes run from small enough to run miniature motors to huge bearings used to support rotating parts in hydroelectric power plants.
In these bearings, the rolling part is a ball, which rolls between inner and outer rings called races. The balls are held by a cage, which keeps them evenly spaced around the races. In addition to these parts, there are a lot of optional parts for special bearings, like seals to keep oil or grease in and dirt out, or screws to hold a bearing in place.
Almost all parts of all ball-bearings are made of steel. Since the bearing has to stand up to a lot of stress, it needs to be made of very strong steel.
The cage for the balls is traditionally made of thin steel, but some bearings now use molded plastic cages, because they cost less to make and cause less friction.
Ball-bearings will be used for many years to come, because they are very simple and have become very inexpensive to manufacture.
Adapted from MADEHOW.COM
ACTIVITY 01: What or who do the underlined words in the text refer to?
