The diagram below shows the use of a lever.

(a) State the principle of moments as applied to the above lever.

(b) To which class of lever does it belong? Give an example of this class of lever.

(c) If FA = 10 cm, AB = 490 cm,

calculate:

(i) the mechanical advantage, and

(ii) the minimum effort required to lift the load (= 50N).

A fire tongs has its arms 20 cm long. It is used to lift a coal of weight 1.5 kgf by applying an effort at a distance 15 cm from the fulcrum.

Find:

(i) the mechanical advantage of fire tongs and

(ii) the effort needed.

The mechanical advantage of an ideal single movable pulley is:

1. 1
2. 2
3. less than 2
4. less than 1.

Which of the following statements is incorrect?

1. The velocity ratio of a single fixed pulley is always 1.
2. The velocity ratio of a single movable pulley is always 2.
3. The velocity ratio of a combination of n movable pulleys with a fixed pulley is always 2ⁿ.
4. The velocity ratio of a block and tackle system is always equal to the number of strands of the tackle supporting load.