(a) What is meant by an ideal machine?

(b) Write a relationship between the mechanical advantage (MA) and velocity ratio (VR) of an ideal machine.

Define work. State the conditions when the work done by a force acting on a body is zero.

Why should a fuse with defined rating not be replaced by one with a larger rating?

If the refractive index of air with respect to glass is expressed as $^g\mu_a = \dfrac{\text{sin i}}{\text{sin r}}$ answer the following:

(a) Express the similar expression for $^a\mu_g$ in terms of i and r.

(b) If angle r = 90°, what is the corresponding angle (i) is called?

(c) Write down the physical significance of angle (i) in part (b).