A running man has the same kinetic energy as that of a boy of half his mass. The man speed up by 2 m s -1 and the boy changes his speed by x m s -1 , so that the kinetic energies of the boy and the man are again equal. Then x in m s -1 is
A
-2 
B
+2 
C
D
2
Text Solution
Verified by ExpertsThe correct answer is:
B
Let vm be velocity of man of boy, then kinetic energy according to question,
i.e. 
or 
When man speeds up 2 m s -1 and boy changes his speed by x m s -1 .Then,
or 
or 
or 
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