1. Tardigrade
  2. Question
  3. Physics
  4. A body of mass 1 kg is taken from infinity to a point P. When the body reaches that point, it has a speed of 2 ms -1. The work done by the conservative force is -5 J. Which of the following is/are true (assuming non-conservative and pseudo-forces to be absent)?

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Q. A body of mass $1 \,kg$ is taken from infinity to a point $P$. When the body reaches that point, it has a speed of $2\, ms ^{-1}$. The work done by the conservative force is $-5\, J$. Which of the following is/are true (assuming non-conservative and pseudo-forces to be absent)?

Work, Energy and Power

Solution:

$\Delta KE =\frac{1}{2} m v^{2}=\frac{1}{2} \times 1 \times 2^{2}=2 \,J$
$W_{\text {cons }}=-\Delta U=-5\, J$
$\Rightarrow \Delta U=5\, J$
$W_{\text {ext }}=\Delta U+\Delta KE =5+2=7\, J$