A person brings a mass of 1kg from infinity to a point A. Initially th

1.	A person brings a mass of 1kg from infinity to a point A. Initially the mass was at rest but it moves at a speed of 2m/s as it reaches A. The work done by the person on the mass is —3J. The potential at A is(a) -3J/kg (b) -2J/kg (c) -5JAg (d) none of these.
Answer» The correct answer is (c) -5 J/kg EXPLANATION: Work done by the person = -3 J (Given) Work done in increasing the velocity from rest to 2 km/s = K.E. of the mass at A =½mv² = ½12² = 2 J Let the potential at A be X J/kg, So, the change in P.E. of the mass = the work done in slowly bringing the mass from infinity to A = mX = 1*X = X J So the total work done = Change in P.E + Change in K.E. = X+2 J, but it is given -3 J so, X+2 = -3 →X = -3-2 = -5 J

A person brings a mass of 1kg from infinity to a point A. Initially the mass was at rest but it moves at a speed of 2m/s as it reaches A. The work done by the person on the mass is —3J. The potential at A is(a) -3J/kg (b) -2J/kg (c) -5JAg (d) none of these.

Answer»

The correct answer is (c) -5 J/kg

EXPLANATION:

Work done by the person = -3 J (Given) Work done in increasing the velocity from rest to 2 km/s = K.E. of the mass at A =½mv² = ½*1*2² = 2 J Let the potential at A be X J/kg,

So, the change in P.E. of the mass = the work done in slowly bringing the mass from infinity to A = mX

= 1*X = X J

So the total work done = Change in P.E + Change in K.E. = X+2 J, but it is given -3 J so, X+2 = -3

→X = -3-2 = -5 J

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A person brings a mass of 1kg from infinity to a point A. Initially the mass was at rest but it moves at a speed of 2m/s as it reaches A. The work done by the person on the mass is —3J. The potential at A is(a) -3J/kg (b) -2J/kg (c) -5JAg (d) none of these.

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