Diagram 1.1 shows a trolley moving down an inclined plane. The ticker timer vibrates at frequency 50Hz.
(a) Underline the correct answer in the bracket to complete the sentence below. The type of current used in the ticker timer is (direct current, alternating current).
Diagram 1.2 shows the ticker tape produced by the motion of the trolley.
(b) Based on Diagram 1.2, (i) one tick is represented by the time taken from point ____ to point ____ .
(ii) compare the distance between PQ and ST.
(iii) state the type of motion of the trolley.