What care would you take to increase the life span of a machine which you use?

Select the correct statement :

(a) A wheel barrow is a lever of class I.

(b) The efficiency of a machine is always 100%.

(c) Friction in moving parts of a machine reduces its efficiency.

(d) No lever has the mechanical advantage greater than 1.

(e) It is easier to lift a load vertically up than to push it along an inclined plane.

(f) A screw is made by two inclined planes placed together.

Describe three orders of levers giving an example of each. Draw neat diagrams showing the positions of fulcrum, load and effort in each kind of lever.

Draw diagrams to illustrate the positions of fulcrum, load and effort, in each of the following :

(a) a see-saw

(b) a beam balance

(c) a nut cracker

(d) a pair of forceps