A car of mass 120 kg is moving at a speed 18 km/h and it accelerates to attain a speed of 54 km/h in 5 seconds. Calculate:

(a) the work done by the engine.

(b) the power of the engine.

(a) A coin kept inside water [µ=$\dfrac{4}{3}$] when viewed from air in a vertical direction appears to be raised by 3.0 mm. Find the depth of the coin in water.

(b) How is the critical angle related to the refractive index of a medium?

(a) Infrared radiations are used in warfare. Explain with reason, why.

(b) A ray of light is incident at 45° on an equilateral prism in the diagram below.

1. Name the phenomenon exhibited by the ray of light when it enters and emerges out of the prism.
2. State the cause of the above phenomenon mentioned by you.

A metre scale of weight 50 gf can be balanced at 40 cm mark without any weight suspended on it.

(a) If this ruler is cut at its centre then state which part [0 to 50 cm or 50 to 100 cm] of the ruler will weigh more than 25 gf.

(b) What minimum weight placed on this metre ruler can balance this ruler when it is pivoted at its centre?