(a) (i) What is a machine?

(ii) State two uses of gears.

(iii) Define the velocity ratio for a pair of gear wheels.

(iv) How can the mechanical advantage of a gear system be increased?

The diagram above illustrates the gears system of a bicycle.

(i) Determine its velocity ratio.

(ii) If the bicycle has an efficiency of 90%, calculate the effort required to overcome a load of 70N.

(iii) Why is the calculated effort less than the actual effort required?