If you wanted to demonstrate a first class lever system to your peers which Childhood toy would you use as a basis for your demonstration and which body motion would you use as an example? A. A yo-yo and handshake
B. A see-saw , chin raise
C. A swing set , a leg kick
D. A slide, a squat

Option B.

A see saw, chin raise.

Explanation:

A lever is a machine that can rotate and consist of a beam which is pivoted to fulcrum.

There are three classes of lever, the first class lever, second class lever and third class lever. These three classes of lever are classified base on the positions of effort, fulcrum and Load.

In first class lever, fulcrum comes between the effort and load. Examples is scissors , see saw, pliers. This is because effort is applied on the one side of the fulcrum and load is on the other side. Therefore, the childhood demonstration of first class lever motion is see saw and chin raise.

In the second class lever, load come between effort and fulcrum e.g wheelbarrow, bottle opener.

In the third class lever, effort comes between fulcrum and load e.g hammer, broom.

the correct answer is - d. china has a large and growing population.

the fact that china has a large (the biggest) population, and it is still growing, doesn't hinder the agriculture production in the country. in fact, it can for increased production in the agriculture, since there's more labor force, as well the sheer mass of people produces lots of scientists that come up with new inventions as to how to improve this sector. nice example is the inner mongolia region in china, in general dominated by the gobi desert, but few scientist came up with a nice idea as to how to make the region productive by using plants that are very resistant to droughts, so lots of people have been employed, and the region is becoming greener and greener each year, and the production of food in this region is also increasing.