Question

A body of mass `1kg` is taken from infinity to a point P. When the body reaches that point, it has a speed of `2ms^-1`. The work done by the conservative force is `-5J`. Which of the following is true (assuming non-conservative and pseudo-forces to be absent).
A. (a) Work done by the applied force is `+7J`
B. (b) The total energy possessed by the body at P is `+7J`
C. (c) The potential energy possessed by the body at P is `+5J`
D. (d) Work done by all forces together is equal to the change in kinetic energy.

Answer 1

Correct Answer - A::B::C::D
`DeltaKE=1/2mv^2=1/2xx1xx2^2=2J`
`W_(cons)=-DeltaU=-5JimpliesDeltaU=5J`
`W_(ext)=DeltaU+DeltaKE=5+2=7J`