Define each of the following reaction mechanism, giving its distinguishing characteristics a) direct reaction; b) compound nucleus reaction; c) pre-equilibrium reaction; d) heavy-ion reaction, and in each case give an example of the nuclear reaction described.

The stopwatch used by a student to measure velocity of a pulse in a slinky was of least count 0.1 second. he stops the stopwatch when a pulse has made 3 journeys from one end to the other of the slinky. he finds the seconds hand to be at 52nd division. calculate the correct time noted by him.