(i) Define critical angle.

(ii) State one important factor which affects the critical angle of a given medium.

The diagram below shows a claw hammer used to remove a nail:

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

(ii) Give one more example of the same class of lever mentioned by you in (i) for which the mechanical advantage is greater than one.

(i) Name the physical quantity which is measured in calories.

(ii) How is calorie related to the S.I. unit of that quantity?

(i) Define couple.

(ii) State the S.I. unit of moment of couple.