(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.