(a) (i) Explain latent heat.
(ii) State two factors that affect the rate of evaporation of a liquid

                    
(b) Explain each of the following observations:
(i)  On a dry day, water in a clay pot is cooler than water in a closed plastic container;
(ii) Food gets cooked faster in a pressure cooker than in an ordinary cooking pot.                  

                                                 
(c) State two effects of heat on a substance.  

                                         
(d)  A 40 V electric heater is used to supply a current of 12 A for 1400 s to a body of mass 1.5 kg at the melting point of the body.  The body melts and its temperature rises through 60\(^o\)C in an extra 72 s.  Determine the:
(i) latent heat of fusion of the body;

(ii)specific heat capacity of the body.  

(a) (i) Define force and state its S.I unit.
(ii) List the two types of solid friction.                                        
(b) A car travelling at a constant speed of 30 ms-1 for 20 s was suddenly decelerated when the driver sighted a pot-hole.  It took the driver 6 s to get to the pot-hole with a reduced speed of 18 ms-1.  He maintained the steady speed for another 10 s to cross the pot-hole.  The brakes were then applied and the car came to rest 5 s later. 
(i) Draw the velocity-time graph for the journey.
(ii) Calculate the deceleration during the last 5 s of the journey.

(iii) Calculate the total distance covered. 

The diagram above illustrates a structure of a typical photocell.

(i)  Identify each of the parts labelled A and B.
(ii) State one function each of A and B
(iii) Einstein’s photoelectric equation can be written as E = hf – Wo.  State what each of the terms E, hf and Wo represent.           
(b) A photon is incident on a metal whose work function is 1.32 eV.  An electron is emitted from the surface with a maximum kinetic energy of 1.97 eV. Calculate the frequency of the photon. [1 eV = 1.6 x 10-19 J]                                                 
(c)(i) Define half-life of a radioactive element.
(ii) Sketch a graph of the relation N = Noe-λt and indicate the half-life.         

A few grains of table salt were put in a cup of cold water, kept at constant temperature and left undistributed. Eventually all the water tested salty. This action is due to?

The force required to make an object of mass m, travelling with velocity v, turn in a circle of radius r is