A 4 m long rod of negligible weight is supported at a point 125 cm from its one end and a load of 18 kgf is suspended at a point 60 cm from the support on the shorter arm.

(a) If a weight W is placed at a distance of 250 cm from the support on the longer arm to balance the rod, find W.

(b) If a weight 5 kgf is kept to balance the rod, find its position.

(c) To which class of lever does it belong?

A lever of length 9 cm has its load arm 5 cm long and the effort arm is 9 cm long.

(a) To which class does it belong?

(b) Draw diagram of the lever showing the position of fulcrum F and directions of both the load L and effort E.

(c) What is the mechanical advantage and velocity ratio if the efficiency is 100%?

(d) What will be the mechanical advantage and velocity ratio if the efficiency becomes 50%?

The figure below shows a wheel barrow of mass 15 kg carrying a load of 30 kgf with its centre of gravity at A. The points B and C are the centre of wheel and tip of the handle such that the horizontal distance AB = 20 cm and AC = 40 cm.

Find:

(a) the load arm,

(b) the effort arm,

(c) the mechanical advantage, and

(d) the minimum effort required to keep the leg just off the ground.

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).