Invented by Archimedes around 250 BC, a Block is a set of pulleys on an axle in a housing. When rope is run through a block or a series of blocks, the whole assembly is called a Tackle. The most common arrangement is to have one1 block attached to a fixed position and another block left to move with the load being pulled or lifted. The mechanical advantage of a block and tackle is equal to the number of time the same line is attached to or runs through the moving block. The pulley on the left does not have a block on the Bale. When you pull on the rope, you are pulling the full weight of the bail. The tackle on the right has 4 lines running through its pulleys. This would allow you to lift 20 pounds with only about 5 pounds of pressure on the hauling part of the line. While the block and tackle is still used today, it has been largely replaced with the electric winch.
The rope used in the 1800's would have been of natural fiber like we have in this exhibit. The rope around the bail is made of SISAL which comes from the leaves of the agave plant. Cotton rope is running in the blocks. Notice how soft it is compared to the SISAL fiber rope. Jute fiber twine, from the Corchorus plant, is used to tie the ends of the larger ropes. It is the same fiber woven to make burlap sacks. Natural fiber rope continued to be in widespread use until the 1950s when synthetic fibers, such as nylon, became popular.
Answer: premaxilla bone (or maxilla) and the maxillary beak (or rhinotheca).
Explanation:
The beak is composed of keratin, the same tough, insoluble protein found in fingernails, hoofs, antlers and horns. A bird's bill comprises two parts. The upper portion of a bird's bill is called the maxillary rostrum, which consists of the premaxilla bone (or maxilla) and the maxillary beak (or rhinotheca).
Answer:
three to six months
Explanation:
According to BBC Science Focus, biodegradable plastics take only three to six months to fully decompose, far quicker than traditional plastic that can take hundreds of years.
Androgenous behaviors is not solely the product of biological sexual
differences, such as the ability to bear children. It is also regarded as product of evolution
and natural selection where an individual may be androgynous, displaying feminine and
masculine characteristics or traits based on one’s gender identity and learned
gender role. This can be made possible through the ongoing social interactions
that individuals have with each other.
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