A negative of a vector represents the direction opposite to the reference direction. It means that the magnitude of two vectors are same but they are opposite in direction.
For example, if A and B are two vectors that have equal magnitude but opposite in direction, then vector A is negative of vector B.
If vectors are arranged as trigonal planar and have equal magnitude, it is an ideal case of zero resultant.
Time taken (t) = 3 sec
Velocity of sound (v) = 332 m/s
Distance travelled (d) = ?
We know,
d = v x t = 332 x 3 = 996 m
Hence, the source of thunder is about 996 m far from the boy.

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The difference between Gram atomic mass and Gram atomic molecular are given below:

The Rh factor(the Rhesus factor or Rh antigen), is a protein that can be found on the surface of red blood cells. It is one of the most important blood group systems in human blood typing. The presence or absence of the Rh factor is denoted as either Rh-positive (+) or Rh-negative (-).
Fun fact: The Rh factor is named after the Rhesus monkey, in which the protein was first discovered.