Work Energy And Power Question 321
Question: A person brings a mass of 1 kg from infinity to a point ‘A’. Initially the mass was at rest but it moves at a speed of 2m/s as it reached A. The work done by the person on the mass is -3J. The potential at ‘A’ is:
Options:
A) $ -3J/kg $
B) $ -2J/kg $
C) $ -5J/kg $
D) none of these
Show Answer
Answer:
Correct Answer: C
Solution:
[c] $ W=(U _{f}-U _{i})+(K _{f}-K _{i})=m(V _{f}-V _{i})+(K _{f}-K _{i}) $ $ -3=1(V _{A}-0)+\frac{1}{2}\times 1\times {{(2)}^{2}}-0 $
$ \therefore $ $ V _{A}=-5J/kg $
